Building on the somewhat recently added Pie-Menu support, Shortcut Composer enables you to utilize pie menus for several functions.
Shortcut Composer is a free and open source source extension for Krita written in Python that make several UI improvements to Krita. The popular open source drawing/paint application Krita has come a long way over the last few years, but using the add-on Shortcut Composer it can be made so much better.