On Ubuntu 16.04 LTS I have used simple keyboard shortcut to set property Always on Top (Nautilus window as example):
In standard Ubuntu 18.04 LTS I can press Alt+Space:
but it does not react to t.
Seems to be a real bug 1710421 since 17.10.
How to enable such menu accelerators/mnemonics in standard Ubuntu 18.04 LTS?