To Customize Subscription resources and permissions in Plesk, Please follow the following settings:-
1) Login to Plesk control panel.

2) Click on "Subscription".
3) Click on "Subscription"

4) Click on Customize button:

5) Click Resources Tab for Change and allocate Disk space, Traffic, Mail, Database and etc.

6) Click Permissions for Enable and disable DNS, Mail management and etc.

7) Click Ok or Unlock & Sync.