Thank you thank you thank you, Blaise.The links you offered eventually led me to the 2008 page that actually explained things most clearly to me. It's not limited to GNOME, I've happily implemented it under KDE. Now I don' t need to switch layouts or rely on dead keys.I've mapped the Compose key to Right-CTRL and all is good. (tried mapping to "menu" but I think that's hardwired to a function and wasn't mappable.)I also find that the Linux equivalent to the Windows Alt-code trick (ALT+0XXX to give any Unicode character) has an equivalent on Linux (Ctl-Shift-U) but it doesn't work reliably on all apps. I have no idea why this is.But no matter. Most of what I want can now be done easily using my newly-mapped Compose key. Guess it can't be a standard location because there is still a diversity of hardware keyboard layouts out there.In any case, thanks again. I leave it to the GTALUG organizers whether this topic merits a tutorial at a meeting.