fixed position add modifier dropdown, or dropdown alternative.

the dropdown box to add a new modifier at the top of the modifiers panel should be fixed, so that it doesn't go out of view when you scroll down the modifier stack. Otherwise you have to scroll all the way back up to the top to add a new modifier.

Alternatively, and probably better, the dropdown should be replaced by a popup window which lists all available modifiers, the user could then drag them from the popup to the location in the modifier stack they'd like to place the new modifier.