Alright, this is almost ripe for merging after six months of intense work:
https://codeberg.org/McCLIM/McCLIM/pulls/1477
It is a new input editing implementation written from scratch for #McCLIM, including a rewrite of completions and accepting values abstraactions.
If you have time and energy then please give it a try and report issues before it is merged. After testing and adding new chapters to the manual I'm planning a new release.