You can make the create button conditional in any portal table. This can be useful in many scenarios, like limiting creation to certain types of users (e.g. active, no outstanding payments, no open applications etc). To set this up, go to:
Your portal's configuration
Select the table you want to limit record creation for
Go to the Create & Expand Records section
Make sure Allow users to create new records is turned on
Turn on Conditional Record Creation
Add conditions as needed
Repeat steps 2 - 6 for each table, if necessary.
This feature is only supported in Portals. It is not available for Interfaces.