RapidWeaver Stacks add-on info:
Create floating stacks: Floating button bars, floating header bars, floating buttons, floating almost anything. The FixMe stack allows you to fix stack with great precision. Add borders and soft shadows. Responsiveness: Hide or release the float on small screens below a breakpoint of your own choice.
The FixMe stack also has a couple of options making it easier to work with fixed stacks – for instance you can hide the floating stack in edit with one click. Very handy when you need to work with the content beneath!
RapidWeaver, stacks, responsive, float, sticky, fixed position.