Yes, filling in 0 for Z works, but ... having a shorcut key to do this would simplify life so much, especially when you often use standard objects (via the suitable plug-in) to then add modifiers to parts of the print. You don't want those modifier objects to always be on the build-plate, so you have to turn off the "automatically drop to build-plate" option, but then for the actual printed parts, you do want them on the build-plate, so ... a shortcut (may I propose CTRL-SHIFT Z) would really be appreciated.