Hi Simon,

This might be of interest, later on.

[removed two video links as they may be only valid with older versions v3/v4 and confuse]

"Custom UI Plugin" (not a 'skin' just extra functionality)
https://moi3d.com/wiki/MaxScriptArchive (top of page "customui")

https://www.youtube.com/watch?v=rm1v-PmhKNI

I think you can fairly easy add your icons on the bottom using custom ui.

Cheers