Convert restrict pro (WP Plugin) checklist into a dropdown

We are using WP Restrict Pro plugin on our website
https://restrictcontentpro.com/

Our page
https://faculti.net/upgrade/

however it is in a checklist form, and occupies to much space, we'd like to convert this into a dropdown option for premium membership selection - WITHOUT LOSING ANY OF THE FUNCTIONALITY

Plugin developer docs:
https://help.ithemes.com/hc/en-us/sections/360009399013-Developer-Docs-Actions

Plugin registration form docs:
https://help.ithemes.com/hc/en-us/articles/360053124813-Creating-Custom-Registration-Fields