I'm trying out the new forms designer on an internal build to try and get the hang of it and I've come across something I'm trying to do that I can't quite figure out. I'd like to dynamically populate a dropdown in the form based on the values input into a collection of single line fields earlier in the form. The setFieldValues in the LFForm object doesn't work for this - it will only set the selected value based on values that are already in the dropdown.

I'm finding it impossible to target anything correctly using jQuery and I'm assuming this is due to wanting us to use the LFForm object but I'm not seeing a way to do what I want to do. I'm wondering if anyone else has had any luck coding something like this or similar using the new designer? (This would be easily done in the classic designer so I might have to switch over to it if none of what I want to do is available in the new designer, but I'd like to work with it since it was implied that classic designer will be removed at some point).