I’d like a ‘razor’ tool so I can chop a region in two by clicking on it. It should also align to whatever snap options I have selected.
Of course if there’s already a way to achieve this, please tell me! 
ardour tries to avoid lots of tools because it slows down the workflow. rather than have a different tool for each operation, we try to make each mouse mode do as much as possible.
in your case, a quick perusal of either the manual or the article on the new editing mode shows that "s" will split regions at the position pointed to by the mouse (subject to snap options). the article explains in more detail which regions will be affected etc.
the manual page is slightly out of date, by the way, and will be updated later today to reflect changes in 2.2.
Thanks paul. I completely agree with you about the need to minimise the number of tools. I’ve never been a big fan of keyboard shortcuts because I always forget them - my keyboard is usually tucked out of the way to make space for my, er, keyboard (of the musical variety) hence I tend to ignore anything related to the keyboard in manuals. Now I’ve read your link I’m seeing the benefits - the ability to act on multiple regions with one keypress for instance. I shall print that link out and stick it to the wall :-).