How to use map() in computed column and related table

I have a table with a relation (1:N). I want to create a computed column with all the names of the related records.
I am getting my data from Xano therefore it seems I cant just use rollup or lookup column functionallity.
My related table is called techDevice. So far I tried map(techDevice,(el)=>{el.devicename}) and under the formula I have the error reading

Position 20: Invalid left hand side of assignment operator =

I also tried the formula map(techDevice,function (el){return el.devicename}) and get this message:

Position 29: Parenthesis ) expected

Also tried (el)=>{el.devicename}) etc but same errors.
I have no clue how to do this but there must be a way.

I have to say the letters in the formula field are so small and blurry, to the point where you almost can’t tell the difference between a square bracket and a pointed bracket. Also features like syntax highlighting and code completion are mostly missing. Overall there could be more hints on whats available etc.