Bug when adding multiple keys to input map

[IndieQuest]

Godot version:
v4.0.dev.custom_build.93b107ac9

OS/device including version:
Windows 10, Nvidia 1070

Issue description:
When adding multiple keys in succession a new input binding is created with the name of the last entered key (see video).

Steps to reproduce:

1. Open project settings
2. Go to the input map tab
3. Create a new action
4. Add A as a key for the new action
5. Without pressing anything else, add the S key to the same action

Minimal reproduction project:
Test.zip

[IndieQuest]

Just saw that the video I attached is corrupted.
Adding an new one with some more examples and behaviors regarding this issue.
BTW, I could not find the relevant code that handles input mapping but if you could point me to it I would love to take a swing at fixing the issue.
InputMapBug.zip

[akien-mga]

The relevant code should be in editor/input_map_editor.cpp.

[IndieQuest]

I am able to conclude that in some cases the TreeItem sent to this function is referencing the first child of the actual action instead of the action itself.
This is the first time I am working with the editor code so I am not yet familiar with how everything works, will continue working on this tomorrow.

[EricEzaM]

That is pretty weird - I have worked quite a bit with the editor code and just a warning, this may not be trivial to solve.

FYI I am in the middle of a bit of a rewrite of the input map editor, I actually remove input_map_editor.cpp and replace with with another, more generic implementation that is not dependant on Project Settings and thus could be used elsewhere if required in the future. It adds UI to expose #43662 to the user interface, and it is partially dependent on #43663 getting merged.

Here is a preview of what it looks like. Since I did a complete rewrite this bug does not seems to be there.

[pouleyKetchoupp]

For info, I've spotted a similar bug when adding keys to multiple actions in a row: #44227.