I've got four sign-related operators: determine sign (-1 / 0 / 1), to positive, to negative, and take sign from another number. For strings they're determine case, to upper case, to lower case, and take case from another string. What about arrays?
Maybe I'll do sorting related stuff. I did have sorting as a separate code point so you could sort characters in a string, but is sorted, sort minimum, sort maximum, take sort from other array could be useful
Maybe vectorization would work, but it doesn't seem particularly useful
There's already a way to vectorize any command with one byte
For the read and write multidimensional commands, are you just indexing into an array (and replacing the element there)? If so, you could just treat the string as a 1-D array
I've got some other operators that work with reading/writing at positions in strings, although maybe doing so but treating the string like a 2d array would be useful
Actually the string square thing shouldn't need its own code point, I've already got an operator to group into strings with length n, so you'd just need to join them