I have a new installation of Ubuntu 18.04 dual boot with Windows 8.1, with (GNOME) Tweaks installed, I need compose key to type Brazilian accent words (à á ã ç), so I installed Tweaks, "US intl with dead key" keyboard layout and followed the instructions on this post. I don't have Scroll Lock, so I tried with PrtScn & right-Alt, none of them worked.
This is the key sequence, compose key (PrtScn or right-Alt) + ' + c, did not work, changed the sequence to compose key (PrtScn or right-Alt) + c + ' both gave me c.
Am I missing some steps?