Assuming your base looks like this:

Then you could set up an automation like so:

It takes all of the records the user selected and uses them in a repeating group, and for each of the selected records it pastes the value from the text field 'New category' into the 'Select' field, which creates a new select option and applies it

Link to base

Hi,

Thanks for your reply. The only issue I cant address with this is that the New Category overwrites the existing values in the Select field. I wish to add the New Category to the ones before. I cannot add them both as tokens in the automation's dynamic configuration as they are two fields in two different pages, the New Category is in page From Submission and Select is in page Record. Is there a way to address that?

Thanks

Hmm, if you're okay with the possibility of a blank option like so:

Then you could set up your automation like this:

Getting rid of the blank option's possible, but would require a small script.  Lemme know if that's something you'd like and I'll see what I can do!