Yes you can do it. but the way you have to do is little bit different. 

FSM allows multiple custom/user define values to be entered. normally it allows 25 user define values for string, 5 for numeric and 5 for dttms. do you need something more? if yes you can use custom metadata.

for the menu, most of the menus are configurable, you can add new items, remove existing items from global code or code table or FSM code table. 

I hope this helps to you

Thank you for clear information.