Add/Remove appication from MATE Applications drop down menu

[Richard Owlett <rowlett@cloud85.net>]

My first problem is there are too many games cluttering the Games 
sub-menu. How to delete selected games from the menu without removing 
the executable?

My second problem is I do not use Firefox. I wish to replace it with a 
non-Debian executable [SeaMonkey].

I've seen instructions somewhere [can't recall where] for adding an 
application to a sub-menu.

TIA