A mode that - no matter the preconfigured panel parameters - launches an app with no panel initially visible.

Basically just a shorthand for:

initialPanels <- DataFrame(Name=character(0), Width=integer(0), Height=integer(0))
iSEE(..., initialPanels=initialPanels)

I would expect this to become a popular mode to launch "empty" apps rapidly (as there are no plots to render) with users adding necessary panels, in contrast to the current behaviour of iSEE() which generates a panel of each type (time consuming) with users removing panels (wasting more time rendering the interface again).

Note: Incidentally, if we're thinking of implementing more modes, I also propose to rename modes mode_<name> (snake_case), in contrast to the current mode<Name> (camelCase). Opinions?