Hi @pozlu0 Thanks for the question and using the Microsoft Q&A platform.
If I understand correctly you want to know if it s possible to assign permission on a SQL table on an SQL Managed Instance
Yes, you should be able to grant or deny object-level permissions. You could take a look here GRANT Object Permissions (Transact-SQL) - SQL Server | Microsoft Learn
General permissions information for the Engine is here Permissions (Database Engine) - SQL Server | Microsoft Learn