Can't organize timelines/etc into subfolders - they can't be moved or disappear from editor

[estherflails]

The problem

Describe the bug
When trying to move timelines/characters/values/themes into empty subfolders, I get this error:
res://addons/dialogic/Other/DialogicUtil.gd:381 - Invalid get index '5' (on base: 'Array').

If I create a new timeline/character/etc directly in the subfolder, I can (mostly) move other ones in and out of it. I can move them out by dropping them above the subfolder, like this:

and sometimes when doing this, they get deleted instead of moved out and I get this error:
res://addons/dialogic/Other/DialogicUtil.gd:399 - Invalid get index 'editortype' (on base: 'Dictionary').
This also sometimes happens when dropping files there that are already in the main folder.

The files in the system folder seem not to have been actually deleted, they just don't show up in the editor. Not sure if all of them just disappeared or if any actually got deleted, though. I tested a bit with reloading the project after saving and the disappeared timelines showed up again in their original location, but I still have a bunch more files in the project folder that are nowhere to be seen in the editor. Perhaps I deleted the folders they disappeared from and that's why they can't show up.

I also noticed from the screenshot above, there's a duplicate timeline in the editor. They also share content. No idea how that happened while I was messing around dropping timelines everywhere. The dupe disappeared after reload.

Edit:
Perhaps related - just noticed that when I quickly open and close folders or subfolders, I get this error:
res://addons/dialogic/Editor/MasterTree/MasterTree.gd:937 - Attempt to call function 'get_metadata' in base 'null instance' on a null instance.

Expected behavior
To be able to move timelines/etc easily into and out of subfolders.

System

• OS: Windows 10
• Godot Version: 3.5.3.stable
• Dialogic Version: 1.5

[zaknafean]

This one is still relevant. More or less the order indexing breaks when there is not already an element in a folder, causing unexpected behaviors.