I guess mIRC already has this code in a couple of places so it shouldn't be too hard to implement at all, but a /popupmenu <menu name> to open a popup menu would be good. This will be great for custom hotlinks and dialogs. No changes will need to be made to the menus, just supply an exist @window menu to open.
Isnt there a keycode that causes the right click menu to appear, I remeber using it once on a machine that had no mouse, but what it is eludes me Could just do a sendkeys!
If you're referring to Shift+F10, it won't work. Pressing Shift+F10 or the 'menu' (or whatever it's called) key pops up the editbox menu, regardless of where the mouse pointer is.