I needed to do this to be able to sort HTML tables. I couldn’t find a way with standard computed columns, so I wrote my own plugin to do it. You’re welcome to use it or clone it.
Actually, because it was primarily written to work with HTML tables, it will need a minor tweak to work for your use case. If you examine the source, in function.js you’ll see the following line (31):
var joined = sorted.join('');
You would just need to tweak that line so that it inserts a delimiter.
Link to use in Glide Code column → Glide Yes-Code
Link to source repo → GitHub - mcdarren/glide-jl-sort-by-keys-advanced
See also: Sort a Joined List using a secondary joined list as sort keys