In unified interface, when you click on the more option button, you will sometimes see the the option to see the related records in the subgrid.
This is handy, especially when you want to see all of the view options, like filters.
But sometimes you might see the “see all records” option instead. This is not very handy, as it shows you all of the records in the related entity, and you don’t have all of the view options.
The reason why you don’t see the “see associated records” option in your subgrid is because you do not have the entity in the subgrid displayed on the navigation area of the form. Add the entity in the subgrid to the form navigation menu/related records are of the form on which the subgrid lives, and you can start viewing your associated records.