Allow Customized Keyboard commands already

Allow Customized Keyboard commands already assigned to be overwritten with a warning.

Currently, if a keyboard shortcut is already assigned you cannot overwrite the command. The workflow for this at present is to find the command it is assigned to and remove it.

Why this is an issue is for beginner users. They want to setup commands to be like other software they have used to help with the transition into MO. They are also not familiar with most of the MO commands. The problem with the current workflow is they often don’t know what the existing command is and therefore do not know how to easily find it.

As per the attached image, F10 key is assigned to 'show'. If the user wants to assign F10 to this command, they need to know the category and the command of 'show' to remove F10 then go back and assign it to the command they want.

I propose that the assign button can be pressed but then a warning shows to state that it will remove the shortcut key for the existing assigned command.