Let me clarify myself, since I obviously made this sound more like a numbered bookmark feature, than a general Geany feature.
There has been several feature requests to include remembered code-folding in Geany, and from the post I linked, there were also a question from the developers on how to handle such a feature if a file was changed. My suggestions above was an attempt to answer that reach-out, giving one possible idea for handling changed files and code folding; of course there are many alternative ways you may want
It is of course possible that Numbered Bookmark developers may include this also for Projects, but I feel that this is a genuinely basic feature which would be great to have in base Geany. Also, hiding the folding in a Plugin that gives its own quirks* which I may not need is not optimal
Is it therefore possible to let this be a Geany request instead of a Plugin request?
Best wishes, and again thanks for the greatest editor on Earth /Jan
* (I do not fancy the Numbered bookmarks that gets in my marigin without me understanding how, and that the bookmarking shortcuts gets in the way of other shortcuts making them impossible to remove. This may be a Mac-Geany problem, I don't know, but at least it does not work as intended for everyone).