I have just updated to 18.04, and cannot right-click and get the little menu to select "Always on top" for Firefox/Chrome, but I can do so for the terminal, pdfs, etc. (along with other things like Minimize, Maximize, Move, etc.) It appears to be a known issue (https://discourse.ubuntubudgie.org/t/18-04-always-on-top-right-click-menu-issues/580), but does not, as far as I can see, have a known fix...
Thoughts appreciated.
Thanks.