I couldn't find it in the manual, is there a way to hide the menubar?
PS I discovered this a few days ago, so awesome! Loved hypercard, and I'll join the decker jam :)
You can hide Decker's menu bar by "locking" a deck. In the main menu, choose "File -> Properties..". and then click "Protect..." to save a locked copy of the current deck.
In the deck file itself, this adds a line like:
locked:1
You can also manipulate whether a deck is locked on the fly by setting "deck.locked" in a script:
on click do deck.locked:!deck.locked end
(Careful, though; if you use scripts to lock a deck you haven't saved yet you might get yourself stuck!)
Edit: oh, and if you meant hide the menu bar while editing, pressing "m" on your keyboard while using drawing tools will temporarily toggle the visibility of the main menu, allowing you to draw "underneath" it.