Keyboard shortcut that send modifier key with a hold duration like 500ms, meanwhile after it holds the modifier key let the cursor move. This will make things so much more efficient.

It also gives lot more flexibility. e.g shift+scroll is commonly used as horizontal scroll, shift+left click is commonly used as multiple selection.

This will be so helpful for some program allows user to hold modifier while using middle button, left button, to send different command, e.g Dopus.

The modifier hold duration can have something like "Caps lock, Num lock, Scroll lock and Fn lock notifications" to remind users. And since it has a duration, a notification that gradually fade out according to the duration would be make sense.

I think the ultimate purpose of a mouse is to avoid using keyboard if not necessary unless searching, typing an essay, using programs for production that really using a lot of shortcut like 3d modelling or video editing