As you probably noticed, Memberstack doesn't allow you to pick what type of field you want to add to your forms. However, if your website builder supports data attributes, we have a workaround for you.
1. Add a select input to your site.
Setup your select field exactly as you would for any other form.
2. Add a new field to Memberstack.
Click Add custom fields on the forms page. After that, select the field and click the Hide from profile toggle so members can't make free-form edits.
3. Add the attribute to your input field.
Save it, and you're ready to test! Memberstack will recognize the selection and save it to the member's profile. That selection will become the new default if a member revisits the form.