As I suggested in the issue, it would be better to save only the scenes in the list, instead of using _save_all_scenes().

@KoBeWi Thanks for your feedback.

I have been reading the code for a while and I found just one reference containing the information of external unsaved files. This tree, calleddisk_changed_list, keeps reference of the string of the scenes names ? (not so sure about it) and I think it is only used for the UI.

Just to be sure you have spotted, calling the _save_all_scenes() does actually the saving scene logic only for the lists that are not saved in the editor _is_scene_unsaved() AND with this pull request scenes that were externally modified _is_scene_externally_modified().

Do you still would prefer a new function like _save_scene(i) that is called somewhere for every externally modified files ? (dont know where or how do you want this function to be called)

Edit :

Reading the code again, I can see that _save_all_scenes() call _save_scene(String, i) for only the scenes that need an update. I see 2 ways of changing it to match what you suggested but I dont see any advantages when compared with what I I have implemented.

Suggestion 1 :
Having another list synchronised with disk_changed_list that keeps track of the index of lists that need to be saved. And then call _save_scene(String, i) for those scenes that needs to be modified.

Suggestion 2:
Having a outer loop (iterating over all scenes) in _resave_scenes() (I would rename it into _resave_externally_modified_scenes()) that checks if a scene needs to be saved and only call the _save_scene(String, i) if it needs to.

_save_scene() already exists and takes a scene path (index is optional), so you can use that.

The reason I think it's better to save only modified scenes is that this information is already available. _save_all_scenes() is used in other places too (e.g. when running project), and with your current code it will perform unnecessary check.

I'd go with your suggestion 1. You can add a LocalVector<String> with paths of the scenes (the same ones as added to disk_changed_list).
Alternatively you can reuse disk_changed_list, since it already has all the scene paths. However it may contain not only scenes, so you'd have to mark items whether they are a scene or not. While it would work, the above solution sounds cleaner.

Note that the project is also saved only if it was externally modified. I assumed that it should work this way.

Thanks!