Add other field with text input to dropdown?

How do I add an other field to a dropdown list that then requires the user to input in a text field that appears?

I recommend you using the Show/Hide Field condition. In this way, when the user selected the "Other" option, a new field will appear. Here's a demo form: https://form.jotformpro.com/71516093777969.

Here's a guide on how I created that demo form:

1. Insert a drop-down field and a short text entry field.

2. Add the "Other" option in the drop-down field.

3. After that, create a Show/Hide Field condition wherein if the user selected "Other", the "Suggestion" text box will appear.

Here's the result:

Related guides:
How-to-Show-or-Hide-Fields-Base-on-User-s-Answer
Hide-or-Show-Multiple-Fields-at-Once

Hope that helps. Let us know if you need any assistance. Thank you.