The way to 'tick all' or 'untick all' on a PC is to click any tune then use the 'edit' menu to 'select all', then right click in the main window and from the little menu that appears, choose to tick or untick all the selected songs.
You can also use the Ctrl key and mouse to select individual groups of songs for ticking or unticking.
I don't know about on a Mac 'cos I don't use one, but I'm sure the Mac must have an equivalent way to perform these operations.