If you want to upgrade your subscription plan, go to Project Central and select the project you want to upgrade.
In the menu shown below, select Subscriptions.
With Projects you are Subscribed to, you can Only Upgrade your Subscription, you cannot Downgrade. If you are already Subscribed to a PRO plan for Example, you will not be able to Downgrade.
Smartapp Overview:
How To?
How To Archive/Restore Projects
Last Updated: Dec-17-20