I set a user permission for user X to supplier A & B only through (Supplier Group).
For the suppliers he can only view Suppliers A & B, but for Purchase invoice and Journal entries he can access all the invoices and Journals of all suppliers.
I want to restrict him to supplier A & B only in anything, how can I do it.
We are using V11
I believe you can use the new user permissions in this context:
How does this work?
For value A
This will restrict the user X to only Supplier A.
Now, to make this restriction for only customer master, and allow access for other doctypes, uncheck Apply to All documents and select the document where this should be applicable (here, customer)
More details in the docs.