Hi
M2_STRLIST with the "l" format option set to 1 could replace M2_COMBO. M2_STRLIST is more powerful and has a dynamic number of elements. Let me know if M2_STRLIST will be ok for your application.
I miss an item type M2_DUMMY , that does not perform visual nothing but only to call a function.
I do not fully understand this. You need something which does not display anything, but will call a function.
Maybe you can describe your desired application for this so that i get a better understanding for this. Also note that there is now an additional callback procedure which might help: http://code.google.com/p/m2tklib/wiki/fnref#setRootChangeCallback
Oliver