Hey @prograds, well the issue checker will tell you. This field accepts a list of numbers. So your expression must not resolve to a list of numbers yet.
Looking at the error from the issue checker will tell you what the expression currently resolves to.
Floppy does not have an action for sorting by other types at present. However, you can use List Shifter to sort some list by some other list (of number, text, or date type).
Somewhere I may have a video showing that, although I may not. Here’s a relevant post though:
Also, this post has a link to another post that includes a link to a 3rd party video about List Shifter’s SORT action;
Hope this helps!