Use this activity to grant all security groups to a permission set for all mobile apps. You can access this option by clicking
the Add All button on the Security Grants by Permission Set page. Once you click the button,
a dialog box will appear asking for confirmation to perform this operation. You can choose either OK to proceed or Cancel to stop.
Refer
to the technical documentation for further details:
Security Groups by Permission Set
As a result of this activity, all security groups are added to a permission set.