Switching apps when presenting on a separate display

Hello,

Any help available here would be much appreciated.

I have the Mac connected to a video projector. Under System Preferences / Displays I have the projector 'mirroring' the Mac's screen.

I have two apps using the Mac's screen : a spreadsheet (in full screen mode) and a Keynote presentation. I would like to be able to choose what is shown on the projector - the spreadsheet or the Keynote presentation - and *easily* switch between the two.

I'm having difficulties achieving this. When I "Play" the Keynote presentation, Keynote seems to get hold of everything : the projector becomes the 'Presentation Display' and the Mac's screen the 'Presenter Display'. If, during the presentation, I need to momentarily display the spreadsheet on the projector, I have to exit the Keynote presentation ('esc') and switch to the spreadsheet on the Mac (the spreadsheet now shows on the projector). On the way back, I have to switch applications on the Mac and press "Play" on the Keynote presentation (the projector now shows the presentation again).

All this is fine except that it is lengthy. It significantly breaks the tempo of the presentation session, the audience gets distracted by what I am doing on the computer, and the focus is lost.

Ideally, I would like to be able to switch what is shown on the projector (Presentation to Spreadsheet to Presentation) with one, or two at the most, mouse clicks. I thought I could do it by just switching applications on the Mac but, unfortunately, when Keynote is "Playing" there is no way to access the Dock to switch applications.

Does anyone know of a combination of Display Arrangement Options, number of Desktops defined on the Mac, Keynote presentation options, ..., that would allow this quick and easy switch ?

Thanks in advance.