@feodor2 Thanks for your new release Mypal 68.14.8b! I am currently testing this version more closely. Due to the complete removal of XUL and XBL, a lot has changed. I have already reported about it here. Similar to version Mypal 68.14.5b, the legacy Custom Buttons extension is no longer fully functional. The internal code editor is totally broken and therefore has become unusable. You can no longer access, view or edit the code with the extension. New custom buttons can't be created, either. The legacy Custom Buttons extension should actually also work in higher Firefox versions. It has corresponding XHTML files and compatible code that is made available via appVersion queries. It could be that an incorrect version is being determined, as version 68 or version 74 is displayed in Mypal 68.14.8b depending on the corresponding command. I checked that in the Browser Console. BTW, I really miss the Scratchpad which is also gone in your new release. Another guess I have is that you have removed something important that requires the legacy Custom Buttons extension. As you know, in Mypal 68.14.7b, the legacy Custom Buttons extension still worked. Maybe, you can take a look at it. BTW, what is the current level of JavaScript and CSS in Mypal 68.14.8b?