To Combine Filters Using a Filter Group in the Level Manager Dialog

In the Level Manager dialog, select Filters in the tree view.
Existing filters are listed.
Click the Create Filter icon.
A new filter appears in the filter list.
Enter the name of the new filter in the Filter name field and press <Enter>.
Select the new filter name.
Right-click and select Filter Group from the pop-up menu.
The Filter Groups dialog opens.

Filter Groups dialog
From the Edit menu, select Insert Filters.
From the Select Filters dialog, select an existing filter, and click OK.

Select Filters dialog
In the Filter Groups dialog, key in a set-based operator: | (or), & (and) , or – (minus).
Select another filter.
If desired, continue to select filters and operators. Click OK when finished.
Note: The & (and) can also be used as the intersection of two sets. For example, if Set A contains 1, 2 and 3 and Set B contains 3, 4 and 5 then Set A & B would contain 3.

Note: The | (or) union of two sets. For example, if Set A contains 1, 2 and 3 and Set B contains 3, 4 and 5 then Set A | B would contain 1,2,3,4,5.

Note: Level Groups created in MicroStation V8 2004 Edition are not backward compatible to earlier versions of MicroStation. For example, if you create a group to a DGN in MicroStation V8 2004 Edition and a group by the same name that was created in a earlier version already exists, the group will only exist during the current session and will not overwrite the old group.