The SalesLine table contains a field called InventDimId, which is a reference to a group of inventory dimensions, that are stored in the InventDim table.
If you need to filter on the warehouse, you will have to filter on a table field, specifically, on the InventLocationId field of the InventDim table.
In order to do this, you will have to join SalesLine and InventDim in your form (2 times, if needed, to 2 different InventDim datasources), and then apply the filter on the datasource field as you would normally