wf-■→□.js

const TARGET = "■";
const REPLACEMENT = "□";

function getAllDescendants(item) {
  const results = [];
  for (const child of item.getChildren()) {
    results.push(child);
    results.push(...getAllDescendants(child));
  }
  return results;
}

function itemNeedsUpdate(item) {
  const containsTarget = item.getName().includes(TARGET) || item.getNote().includes(TARGET);
  return containsTarget && !item.isReadOnly();
}

const descendants = getAllDescendants(WF.currentItem());
const itemsToUpdate = descendants.filter(itemNeedsUpdate);

if (itemsToUpdate.length === 0) {
  WF.showMessage("No matching items found.", false);
} else {
  WF.editGroup(() => {
    for (const item of itemsToUpdate) {
      if (item.getName().includes(TARGET))
        WF.setItemName(item, item.getName().replaceAll(TARGET, REPLACEMENT));
    }
  });

  WF.showMessage(`Updated ${itemsToUpdate.length} item(s).`);
  setTimeout(WF.hideMessage, 5000);
}