(Although some level of misery is hard to get out of with only a touchscreen.)
I have used this keyboard for over a year now I think and it's really good.
I hate long pressing. It's so slow and imprecise.
Ctrl-z to undo is an action usually not available from the context menu or elsewhere.
Oh and pressing ctrl-d to send EOF in a subshell in Termux is much more convenient than typing "exit" or whatever.
So, just a conventional shortcut to close things.
For example, in Python REPL, you can press ^C to interrupt a running piece of code:
>>> while True:
... pass
...
^CTraceback (most recent call last):
File "<stdin>", line 1, in <module>
KeyboardInterrupt
>>> (^C)
KeyboardInterrupt
Ruby's irb works the same (and of course Bash/zsh do, too). In Node.js, ^D works right away, and ^C first triggers a warning but you can press it the second time to exit.
Selecting the appropriate text is already a challenge in so many circumstances. Having to tap again exactly inside the selection, then choose from the floating menu are two more failure points and interaction lag.
It's especially painful when trying to select single characters (which happens a lot in CJK land).
I wish I could join the GBoard team for two weeks, just add an optional ctrl key, and quit.
PS: Actually, mapping the physical Volume Up to Copy, Volume Down to Paste whenever there's no media playing or some other condition could be the best choice.
I just tried on a Galaxy A54, and don't see such an option.