Describe the bug
Hotkey modifiers (alt, shift), are ignored by the open backpack setting. For example, if the control is saved as "SHIFT + e", both "e" and "SHIFT + e" will open the backpack.

To Reproduce
Steps to reproduce the behavior:

1. Open controls
2. Change control to include modifier
3. Test control

Expected behavior
Backpack should only open when correct control is pressed.
Screenshots
If applicable, add screenshots to help explain your problem.

Versions

This just plain works correctly for me (when I set open backpack as SHIFT + e I have to press shift otherwise the backpack won't open) and checking in code proper call is being made which includes mandatory check for modifier key (shift/alt/ctrl). So my guess is that you have a mod included in the modpack that breaks this behavior. You will need to find out which one that is and report to them that they are breaking this behavior.

I think I caused some confusion with my original post. As stated in my previous comment, I am only using the backpack mod. Attached below is a video, with keyboard presses shown to better explain.

So I couldn't recreate, but once I updated forge to your version now I can. It appears to be bug in for for which neoforge has an open fix neoforged/NeoForge#171. Anyway it appears that if you don't have conflicting keybinds (that is in your case not have anything else bound to E in any kind of combination with modifier key which I am guessing will be difficult) the modifiers will work correctly. If you want them to work correctly without resolving these conflicts you will need to downgrade to one of the earlier versions of forge