Dynamics 365 hide New-Button in subgrid for activities

Question

How can I hide the +NEW-Button in a subgrid of activities, when the parent records status is inactive? I tried already to hide this Button with RibbonWorkbench to see if hiding would generally work when I later implement a javascript hide-rule, but the +-Button is still visible. I tried to hide this button on the activitypointer as well as task entity but the +-Button is still visible. Background: Customer should not be able to add new activities, when the paretn record's status is inactive. I followed this tip How to unable create a new record button from sub grid but withou success.

Answer 1

Customer should not be able to add new activities, only view them

If you remove the create privilege for an entity in that user persona security role, then the Add New [+] ribbon button will be hidden automatically. That’s the right approach.