extracted via strings and sanitized for probable/sane arguments that can be passed via a CLI

bin|cef|cef.winxp|steamwebhelper.exe

-no-cef-sandbox
-cef-disable-sandbox
-cef-disable-seccomp-sandbox
-cef-force-sandbox
-cef-verbose-logging
-cef-disable-js-logging
-cef-verbose-js-logging
-cef-single-process
-cef-in-process-gpu
-cef-disable-d3d11
-cef-full-memory-crash-report
-cef-disable-breakpad
-cef-force-32bit
-cef-disable-hang-timeouts
-cef-enable-debugging
-cef-disable-occlusion
-cef-ignore-certificate-errors
-cef-no-linux-angle
-cef-enable-gpu-debugging
-cef-disable-gpu
-cef-delaypageload
-cef-disable-delaypageload
-cef-enable-samesite-by-default-cookies
-cef-winxp

probably-steam-options.txt

-$:r
-480p
-720p
-allosarches
-allosvers
-alwaysrelaunch
-beta
-bootstrapperproxy
-chromeos
-chromeosdiskmanagement
-clientbeta
-clientui
-community
-console
-d?r
-debugbreak
-dev
-download
-exitsteam
-failsystemcheck
-forceguiupdater
-forcejunction
-forceosver
-forcepackagedownload
-forcesteamupdate
-friendsui
-fs_log
-fs_logbins
-fs_target
-full_memory_dump
-fulldesktopres
-gamepadui
-holo
-hometest
-ifrunning
-inf
-inhibitbootstrap
-installupdate
-jqh
-k_EMsgAMIsAccountInCaptchaGracePeriodResponse
-k_EMsgAMTwoFactorRecoverAuthenticatorResponse
-k_EMsgBSResetPackagePurchaseRateLimitResponse
-k_EMsgClientRequestEncryptedAppTicketResponse
-k_EMsgDRMWorkerProcessBackfillOriginalRequest
-k_EMsgDRMWorkerProcessSplitAndInstallResponse
-k_EMsgEnsureExecuteScheduledTaskResponse_TEST
-k_EMsgGMTestNextBuildSchemaConversionResponse
-k_EMsgGSComputeNewPlayerCompatibilityResponse
-k_EMsgPSAddWalletCreditToShoppingCartResponse
-k_EMsgRemoteClientGetControllerConfigResponse
-k_EMsgSMTestNextBuildSchemaConversionResponse
-language
-master_ipc_name_override
-noassert
-nobootstrapperupdate
-noconsole
-nocrashdialog
-nodircheck
-nofriendsui
-noiocp
-noreactlogin
-norepairfiles
-noverifyfiles
-oldlib
-overridepackageurl
-promptdebugattach
-RESERVELOWMEM
-silent
-simulatedownloaderrors
-simulatefatalerror
-singleapp
-skipinitialbootstrap
-steamchina
-steamconsole
-steamdeck
-steamos
-steamos3
-steamrow
-store
-textclient
-timingtestflushdiskcache
-tryjunction
-verifyfiles
-windowed
-X:r
-X:r
-X?r
-X?r

win7x64|libcef.dll

#strings drive_c/Program\ Files\ \(x86\)/Steam/bin/cef/cef.win7x64/libcef.dll | grep '\-sandbox'
gpu-sandbox-start-early
coop-sandboxed-iframe-cannot-navigate-to-coop-page
enable-shill-sandboxing
coop-sandboxed-iframe-cannot-navigate-to-coop-page
disabled-by-default-sandbox
allow-popups-to-escape-sandbox
wallet-service-use-sandbox
service-sandbox-type
allow-no-sandbox-job
disable-gpu-sandbox
disable-seccomp-filter-sandbox
disable-setuid-sandbox
enable-audio-service-sandbox
gpu-sandbox-allow-sysv-shm
gpu-sandbox-failures-fatal
no-sandbox
# strings drive_c/Program\ Files\ \(x86\)/Steam/bin/cef/cef.win7x64/libcef.dll | grep 'disable-'
disable-canvas-aa
disable-2d-canvas-image-chromium
disable-3d-apis
disable-accelerated-2d-canvas
disable-accelerated-video-decode
disable-accelerated-video-encode
disable-backgrounding-occluded-windows
disable-background-timer-throttling
disable-blink-features
disable-databases
disable-domain-blocking-for-3d-apis
disable-webgl
disable-webgl2
disable-file-system
disable-flash-3d
disable-flash-stage3d
disable-gesture-requirement-for-presentation
disable-gpu
disable-gpu-compositing
disable-gpu-early-init
disable-gpu-memory-buffer-compositor-resources
disable-gpu-memory-buffer-video-frames
disable-gpu-process-crash-limit
disable-software-compositing-fallback
disable-gpu-watchdog
disable-ipc-flooding-protection
disable-hang-monitor
disable-histogram-customizer
disable-kill-after-bad-ipc
disable-lcd-text
disable-local-storage
disable-logging
disable-low-latency-dxva
disable-new-content-rendering-timeout
disable-notifications
disable-pepper-3d
disable-permissions-api
disable-pepper-3d-image-chromium
disable-pinch
disable-prefer-compositing-to-lcd-text
disable-presentation-api
disable-pushstate-throttle
disable-reading-from-canvas
disable-remote-fonts
disable-remote-playback-api
disable-renderer-accessibility
disable-renderer-backgrounding
disable-shared-workers
disable-skia-runtime-opts
disable-smooth-scrolling
disable-software-rasterizer
disable-speech-api
disable-speech-synthesis-api
disable-test-root-certs
disable-threaded-compositing
disable-threaded-scrolling
disable-v8-idle-tasks
disable-webgl-image-chromium
disable-web-security
disable-zero-copy-dxgi-video
disable-2d-canvas-clip-aa
disable-yuv-image-decoding
disable-origin-trial-controlled-blink-features
disable-nv12-dxgi-video
disable-oop-rasterization
disable-javascript-harmony-shipping
disable-site-isolation-trials
disable-webrtc-encryption
disable-webrtc-hw-decoding
disable-webrtc-hw-encoding
disable-scroll-to-text-fragment
disable-quick-menu
disable-legacy-window
disable-gpu-rasterization
disable-gpu-process-for-dx12-vulkan-info-collection
disable-audio-output
disable-background-media-suspend
disable-accelerated-mjpeg-decode
disable-rtc-smoothness-algorithm
disable-image-animation-resync
disable-low-res-tiling
disable-partial-raster
disable-rgba-4444-textures
disable-zero-copy
disable-component-cloud-policy
through commandline switch --disable-gpu.
allow-disable-mouse-acceleration
disable-animation-on-low-battery
disable-best-effort-tasks
disable-hosted-app-shim-creation
disable-keepalive-fetch
disable-touch-adjustment
ntp-disable-initial-most-visited-fade-in
omnibox-disable-instant-extended-limit
code-disable-optimization
disable-pack-loading
disable-javascript
disable-javascript-close-windows
disable-javascript-access-clipboard
disable-javascript-dom-paste
disable-image-loading
disable-text-area-resize
disable-tab-to-links
disable-plugins
disable-spell-checking
disable-scroll-bounce
disable-pdf-extension
disable-new-browser-info-timeout
disable-best-effort-tasks
disable-breakpad
disable-features
disable-low-end-device-mode
disable-highres-timer
disable-usb-keyboard-detect
perfetto-disable-interning
disable-oor-cors
disable-threaded-animation
disable-composited-antialiasing
disable-main-frame-before-activation
disable-checker-imaging
disable-layer-tree-host-memory-pressure
disable-d3d11
disable-es3-gl-context
disable-es3-gl-context-for-testing
disable-gpu-driver-bug-workarounds
disable-gpu-vsync
disable-angle-features
disable-gl-drawing-for-tests
disable-gl-extensions
disable-direct-composition
disable-direct-composition-video-overlays
disable-composited-antialiasing
disable-dwm-composition
disable-touch-adjustment
disable-touch-drag-drop
ui-disable-partial-swap
disable-frame-rate-limit
disable-gl-error-limit
disable-glsl-translator
disable-shader-name-hashing
disable-gpu-program-cache
disable-gpu-shader-disk-cache
disable-vulkan-surface
disable-vulkan-fallback-to-gl-for-testing
disable-offer-store-unmasked-wallet-cards
disable-quic
disable-http2
disable-gpu-sandbox
disable-seccomp-filter-sandbox
disable-setuid-sandbox
disable-win32k-lockdown
disable-in-process-stack-traces
disable-audio-support-for-desktop-share
disable-extensions-http-throttling
disable-accelerated-2d-canvas
ui-disable-partial-swap
disable-webrtc-hw-decoding
disable-webrtc-hw-encoding
disable-javascript-harmony-shipping
disable-accelerated-video-decode
disable-accelerated-video-encode
disable-threaded-scrolling
disable-top-sites
optimization-guide-disable-installer
disable-syncfs-on-disk-indexing
disable-auto-reload
disable-background-networking
disable-bundled-ppapi-flash
disable-client-side-phishing-detection
disable-component-extensions-with-background-pages
disable-component-update
disable-default-apps
disable-device-discovery-notifications
disable-domain-reliability
disable-extensions
disable-extensions-except
disable-extensions-file-access-check
disable-print-preview
disable-prompt-on-repost
disable-windows10-custom-titlebar
disable-background-downloads
disable-delta-updates
disable-pings
disable-popup-blocking
disable-dinosaur-easter-egg
disable-signin-scoped-device-id
disable-sync
sync-disable-deferred-startup
disable-video-capture-use-gpu-memory-buffer
disable-sync-types
disable-fetching-hints-at-navigation-start
disable-checking-optimization-guide-user-permissions
disable-native-scroll
disable-native-scroll
force-disable-variation-ids
disable-output-escaping
no-sandbox-and-elevated
wallet-service-use-sandbox
use-sync-sandbox