Different plans come with varying limits on extension creation. Some plans have restrictions on the number of extensions allowed. You can check the homepage of the admin page to see the number of extensions per page.
You can create only one extension of each type.
Only a limited version of the form extension is supported.
The portal extension is not supported.
You can create a maximum of:
5 bulk extensions
There is no limit on the number of child forms in the Plus Plan.
You can create an unlimited number of extensions.