On Screen Menu
First you can find good documentation in MicroStation help: Screen Menus (bentley.com)
And I won't say something better than the first line in the doc:
"As an alternative to using the customized ribbon interface, you can customize the user interface by creating clickable screen menus"
Then don't search the artist in me. No way. So I just give a quick example, nothing really elaborated but could be a first step.
Feel free to use and transform. Should be placed in Standards/dgnlib/gui
OnScreenMenus.dgnlib
Popup menu