To Change Level Symbology Across Multiple Target Files

Select the desired targets from the tree.
The levels from the selected targets display in the level list.
Select the Dialog Settings icon in the Level Manager dialog.
Turn on the Merge Names check box.
Make the desired symbology changes on the desired level(s).
The symbology changed on all selected files in the target tree.

Note: If Merge Names is off and multiple levels of the same name exist, you must make the symbology change on each level of that name.