After doing this in a Firefox extension:

browser.browsingData.remove({"since": 0, "originTypes": {"unprotectedWeb": true, "protectedWeb": true, "extension": true} }, {
  "cache": true,
  "cookies": false,        // I delete them separately
  "downloads": true,
  //"fileSystems": true,   // not available on FF
  "formData": true,
  "history": true,
  "indexedDB": true,
  "localStorage": true,
  "passwords": false,
  "pluginData": true,
  "serviceWorkers": true,
}, function() { 
    console.log('done');
});

everything is successfully deleted (history, etc.), but this is still remaining:

Why? This is not because of cookies (these website have currently 0 cookies, I double checked this).

How to remove everything completely?

Note: I have set "permissions": ["storage", "browsingData", "cookies", "<all_urls>"] in the manifest.