On the values of the Inspector and Project Settings, a progress bar in the background of numerical properties could be displayed. This would add some visual feedback (making visual grepping faster), as well as making adjustements by dragging the mouse more intuitive for users. The latter may require changing the dragging direction for adjustments (since bars are horizontal), though.
As seen in Blender:

This is how it's done in unreal, and both unreal and unity use left/right for dragging rather than up/down, so changing it to match that would also make sense.
While we are at it, wouldn't it make sense to also implement counting up by 1 with the Up-Arrow and counting down by 1 with the Down-Arrow?
Update: As of https://github.com/godotengine/godot/commit/6895ad303b51aaf84a568c982e3622049a50ed37, this is implemented for floats but not for integer values.


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While we are at it, wouldn't it make sense to also implement counting up by 1 with the Up-Arrow and counting down by 1 with the Down-Arrow?