Unicode progress tooltip?

[Skip Montanaro]

I have a US layout keyboard. I occasionally need to type non-ASCII stuff
like ¾, ₤ or é. I've now memorized a few Compose key sequences (environment
is Ubuntu 20.04), but golly gee, there are a lot of them! I noticed that
when I mash down on the Compose key a little tooltip pops up

[image: Screenshot from 2020-10-11 10-59-29.png]

and is extended as more keys are pressed. Once a complete sequence is
entered, the appropriate glyph is rendered and the tooltip dismissed. This
is very nice.

Still, I wonder... Is there a way to get Emacs to display all the
possibilities for the next key and the resulting glyph? This would be sort
of like the long press over a key on my Android phone which brings up a
pop-up menu showing the various related characters you can select. For
example, after entering Compose L, it appears the "next set" only contains
eight characters (according to my computer's Compose file). Is there some
package which can parse the Compose file and present the next characters
and potentially the final possible glyphs? I poked around in the package
list on my Emacs install (v 26.3). None of the packages matching the search
string "unicode" seemed like what I was looking for.

Thanks,

Skip