The logic that is currently implemented in the moveset validator does not check for what the user did wrong, it only checks for what is allowed with the current values. Adding in extra logic to guide the person who made a mistake takes more developer time (& CPU time too). The main goal of the legality checker is to check if things are legal, not to indicate every corrective action (as one size does usually not fit all).
You can select all text in the textbox and copy it to an external notepad editor, or you can check the shortcuts.txt via the source code on GitHub.
This is a Windows Forms application; these kind of apps are for Windows systems but can be run with Wine/etc on Linux and Mac. Certain experiences are not tailored to be multi-platform where right clicking does not exist. Using a virtual machine may help. Not sure how worth it is to make hotkeys/shortcuts configurable, since that would require changing a lot of things around