Unable to hide Add button for child

[Bellave_Jayaram]

I have a use case similar to How can I prevent additional rows being added

The parent table is called Surveys and the child table is Readings. In the Surveys table, I need to

• prevent new child rows being created and
• ALL child Rows to be locked for Edit

when column Last in any row in Readings is set to TRUE.

I am able to hide the Edit button (overlay pencil icon) in the Surveys table using

NOT(IN(TRUE, [Related Readings][Last]))

but when I try to hide the Add button in the inline view of the Surveys detail view and the + action button in the Readings inline table view using this:

NOT(IN(TRUE, SELECT(Readings[Last], [SurveyID]=[_THISROW].[SurveyID])))

it doesn’t hide the Add.

What am I missing? Is this a bug? Anybody else seeing this?

Thanks.