A click on the current tool icon brings up a Popup menu with the six basic tools.
A left click on one of the tools switches to that tool, and a right click exits from the menu leaving the current tool unchanged.
At first sight, six tools sounds rather spartan. However, each basic tool can have its parameters varied so as to produce a special tool for almost any use.
These settings may be stored in a list separately for each basic tool. When switching between basic tools the relevant settings list will be activated as well. All lists may be saved together.
Putting tool and tool parameter selections onto macros makes this process even simpler, since the Popups can be made to appear at the current mouse position (in Calamus "Options", "Miscellaneous", "Dialogs to mouse position").