Having defined a subcollection filter, use the "Assign Partitions" tab to build indexes for it (or for a group of filters). Select the desired filter (or filters) from the "Defined Subcollection Filters" list and click "Add Partition".

To remove a partition, select it from the list and click "Remove Partition".

To make a partition the default one, select it from the list and click "Set Default Partition".

To clear the default partition, click "Clear Default Partition".