Registers Paint.NET (so the .pdn Shell Extension works). You must run regedit as TrustedInstaller to import this (use https://github.com/M2TeamArchived/NSudo for this.

Register_Paint.NET.reg

Windows Registry Editor Version 5.00

; You must run regedit as TrustedInstaller to import this
; Use https://github.com/M2TeamArchived/NSudo to do this

; Application Registration

[HKEY_CLASSES_ROOT\paint.net.1]
@="paint.net Image"
"FriendlyTypeName"="paint.net Image"

[HKEY_CLASSES_ROOT\paint.net.1\CurVer]
@="paint.net.1"

[HKEY_CLASSES_ROOT\paint.net.1\DefaultIcon]
@="C:\\Users\\xjonx\\AppData\\Roaming\\paint.net\\paintdotnet.exe,0"

[HKEY_CLASSES_ROOT\paint.net.1\shell\edit\command]
@="\"C:\\Program Files\\paint.net\\paintdotnet.exe\" \"%1\""

[HKEY_CLASSES_ROOT\paint.net.1\shell\open\command]
@="\"C:\\Users\\xjonx\\AppData\\Roaming\\paint.net\\paintdotnet.exe\" \"%1\""

[HKEY_CLASSES_ROOT\paint.net.1\shell\print\command]
@="\"C:\\Users\\xjonx\\AppData\\Roaming\\paint.net\\paintdotnet.exe\" print:%1\""

[HKEY_CLASSES_ROOT\paintdotnet]
@="URL:paint.net"
"URL Protocol"=""

[HKEY_CLASSES_ROOT\paintdotnet\DefaultIcon]
@="C:\\Users\\xjonx\\AppData\\Roaming\\paint.net\\paintdotnet.exe,0"

[HKEY_CLASSES_ROOT\paintdotnet\shell\open\command]
@="\"C:\\Users\\xjonx\\AppData\\Roaming\\paint.net\\paintdotnet.exe\" \"%1\""

[HKEY_CLASSES_ROOT\CLSID\{FBF113F1-D7C8-477C-A23A-E600E7937E11}]
@="paint.net Thumbnail Provider"

[HKEY_CLASSES_ROOT\CLSID\{FBF113F1-D7C8-477C-A23A-E600E7937E11}\InprocServer32]
@="C:\Program Files\paint.net\PaintDotNet.ShellExtension.x64.dll"
"ThreadingModel"="Apartment"

[HKEY_CLASSES_ROOT\paint.net.1\ShellEx\{E357FCCD-A995-4576-B01F-234630154E96}]
@="{FBF113F1-D7C8-477C-A23A-E600E7937E11}"

[HKEY_CLASSES_ROOT\paint.net.ThumbnailProvider\CLSID]
@="{FBF113F1-D7C8-477C-A23A-E600E7937E11}"

[HKEY_CLASSES_ROOT\paint.net.ThumbnailProvider\CurVer]
@="paint.net.ThumbnailProvider.1"

[HKEY_CLASSES_ROOT\paint.net.ThumbnailProvider.1\CLSID]
@="{FBF113F1-D7C8-477C-A23A-E600E7937E11}"

[HKEY_CLASSES_ROOT\.pdn\ShellEx\{E357FCCD-A995-4576-B01F-234630154E96}]
@="{FBF113F1-D7C8-477C-A23A-E600E7937E11}"

[HKEY_LOCAL_MACHINE\Software\RegisteredApplications]
"paint.net"="Software\\paint.net\\Capabilities"

[HKEY_LOCAL_MACHINE\Software\paint.net\Capabilities]
"ApplicationName"="paint.net"
"ApplicationDescription"="paint.net allows you to create and edit images and photographs using a wide array of tools, adjustments, and effects."

[HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\App Paths\paintdotnet.exe]
@="C:\\Users\\xjonx\\AppData\\Roaming\\paint.net\\paintdotnet.exe"
"SupportedProtocols"="paintdotnet"

[HKEY_CLASSES_ROOT\Applications\paintdotnet.exe\shell\edit\command]
@="\"C:\\Users\\xjonx\\AppData\\Roaming\\paint.net\\paintdotnet.exe\" \"%1\""
"FriendlyAppName"="paint.net"

; File Type Registration

; .pdn

[HKEY_LOCAL_MACHINE\Software\paint.net\Capabilities\FileAssociations]
".pdn"="paint.net.1"

[HKEY_CLASSES_ROOT\.pdn]
@="paint.net.1"
"PerceivedType"="image"

[HKEY_CLASSES_ROOT\Applications\paintdotnet.exe\SupportedTypes]
".pdn"=""

[HKEY_CLASSES_ROOT\.pdn\OpenWithProgids]
"paint.net.1"=""

; .avif

[HKEY_LOCAL_MACHINE\Software\paint.net\Capabilities\FileAssociations]
".avif"="paint.net.1"

[HKEY_CLASSES_ROOT\Applications\paintdotnet.exe\SupportedTypes]
".avif"=""

[HKEY_CLASSES_ROOT\.avif\OpenWithProgids]
"paint.net.1"=""

; .bmp

[HKEY_LOCAL_MACHINE\Software\paint.net\Capabilities\FileAssociations]
".bmp"="paint.net.1"

[HKEY_CLASSES_ROOT\Applications\paintdotnet.exe\SupportedTypes]
".bmp"=""

[HKEY_CLASSES_ROOT\.bmp\OpenWithProgids]
"paint.net.1"=""

; .dib

[HKEY_LOCAL_MACHINE\Software\paint.net\Capabilities\FileAssociations]
".dib"="paint.net.1"

[HKEY_CLASSES_ROOT\Applications\paintdotnet.exe\SupportedTypes]
".dib"=""

[HKEY_CLASSES_ROOT\.dib\OpenWithProgids]
"paint.net.1"=""

; .dds

[HKEY_LOCAL_MACHINE\Software\paint.net\Capabilities\FileAssociations]
".dds"="paint.net.1"

[HKEY_CLASSES_ROOT\.dds]
"PerceivedType"="image"

[HKEY_CLASSES_ROOT\Applications\paintdotnet.exe\SupportedTypes]
".dds"=""

[HKEY_CLASSES_ROOT\.dds\OpenWithProgids]
"paint.net.1"=""

; .gif

[HKEY_LOCAL_MACHINE\Software\paint.net\Capabilities\FileAssociations]
".gif"="paint.net.1"

[HKEY_CLASSES_ROOT\Applications\paintdotnet.exe\SupportedTypes]
".gif"=""

[HKEY_CLASSES_ROOT\.gif\OpenWithProgids]
"paint.net.1"=""

; .heic

[HKEY_CLASSES_ROOT\CLSID\{E9A4A80A-44FE-4DE4-8971-7150B10A5199}\InprocServer32]
@="C:\\WINDOWS\\system32\\msheif.dll"

[HKEY_LOCAL_MACHINE\Software\paint.net\Capabilities\FileAssociations]
".heic"="paint.net.1"

[HKEY_CLASSES_ROOT\Applications\paintdotnet.exe\SupportedTypes]
".heic"=""

[HKEY_CLASSES_ROOT\.heic\OpenWithProgids]
"paint.net.1"=""

; .jfif

[HKEY_LOCAL_MACHINE\Software\paint.net\Capabilities\FileAssociations]
".jfif"="paint.net.1"

[HKEY_CLASSES_ROOT\Applications\paintdotnet.exe\SupportedTypes]
".jfif"=""

[HKEY_CLASSES_ROOT\.jfif\OpenWithProgids]
"paint.net.1"=""

; .jpe

[HKEY_LOCAL_MACHINE\Software\paint.net\Capabilities\FileAssociations]
".jpe"="paint.net.1"

[HKEY_CLASSES_ROOT\Applications\paintdotnet.exe\SupportedTypes]
".jpe"=""

[HKEY_CLASSES_ROOT\.jpe\OpenWithProgids]
"paint.net.1"=""

; .jpeg

[HKEY_LOCAL_MACHINE\Software\paint.net\Capabilities\FileAssociations]
".jpeg"="paint.net.1"

[HKEY_CLASSES_ROOT\Applications\paintdotnet.exe\SupportedTypes]
".jpeg"=""

[HKEY_CLASSES_ROOT\.jpeg\OpenWithProgids]
"paint.net.1"=""

; .jpg

[HKEY_LOCAL_MACHINE\Software\paint.net\Capabilities\FileAssociations]
".jpg"="paint.net.1"

[HKEY_CLASSES_ROOT\Applications\paintdotnet.exe\SupportedTypes]
".jpg"=""

[HKEY_CLASSES_ROOT\.jpg\OpenWithProgids]
"paint.net.1"=""

; .jxr

[HKEY_LOCAL_MACHINE\Software\paint.net\Capabilities\FileAssociations]
".jxr"="paint.net.1"

[HKEY_CLASSES_ROOT\Applications\paintdotnet.exe\SupportedTypes]
".jxr"=""

[HKEY_CLASSES_ROOT\.jxr\OpenWithProgids]
"paint.net.1"=""

; .png

[HKEY_LOCAL_MACHINE\Software\paint.net\Capabilities\FileAssociations]
".png"="paint.net.1"

[HKEY_CLASSES_ROOT\Applications\paintdotnet.exe\SupportedTypes]
".png"=""

[HKEY_CLASSES_ROOT\.png\OpenWithProgids]
"paint.net.1"=""

; .rle

[HKEY_LOCAL_MACHINE\Software\paint.net\Capabilities\FileAssociations]
".rle"="paint.net.1"

[HKEY_CLASSES_ROOT\Applications\paintdotnet.exe\SupportedTypes]
".rle"=""

[HKEY_CLASSES_ROOT\.rle\OpenWithProgids]
"paint.net.1"=""

; .tga

[HKEY_LOCAL_MACHINE\Software\paint.net\Capabilities\FileAssociations]
".tga"="paint.net.1"

[HKEY_CLASSES_ROOT\Applications\paintdotnet.exe\SupportedTypes]
".tga"=""

[HKEY_CLASSES_ROOT\.tga\OpenWithProgids]
"paint.net.1"=""

; .tif

[HKEY_LOCAL_MACHINE\Software\paint.net\Capabilities\FileAssociations]
".tif"="paint.net.1"

[HKEY_CLASSES_ROOT\Applications\paintdotnet.exe\SupportedTypes]
".tif"=""

[HKEY_CLASSES_ROOT\.tif\OpenWithProgids]
"paint.net.1"=""

; .tiff

[HKEY_LOCAL_MACHINE\Software\paint.net\Capabilities\FileAssociations]
".tiff"="paint.net.1"

[HKEY_CLASSES_ROOT\Applications\paintdotnet.exe\SupportedTypes]
".tiff"=""

[HKEY_CLASSES_ROOT\.tiff\OpenWithProgids]
"paint.net.1"=""

; .wdp

[HKEY_LOCAL_MACHINE\Software\paint.net\Capabilities\FileAssociations]
".wdp"="paint.net.1"

[HKEY_CLASSES_ROOT\Applications\paintdotnet.exe\SupportedTypes]
".wdp"=""

[HKEY_CLASSES_ROOT\.wdp\OpenWithProgids]
"paint.net.1"=""

; .wmp

[HKEY_LOCAL_MACHINE\Software\paint.net\Capabilities\FileAssociations]
".wmp"="paint.net.1"

[HKEY_CLASSES_ROOT\Applications\paintdotnet.exe\SupportedTypes]
".wmp"=""

[HKEY_CLASSES_ROOT\.wmp\OpenWithProgids]
"paint.net.1"=""

; .webp

[HKEY_LOCAL_MACHINE\Software\paint.net\Capabilities\FileAssociations]
".webp"="paint.net.1"

[HKEY_CLASSES_ROOT\Applications\paintdotnet.exe\SupportedTypes]
".webp"=""

[HKEY_CLASSES_ROOT\.webp\OpenWithProgids]
"paint.net.1"=""