Problem

How to use reference file level symbology overrides without affecting the active file levels.

Solution

Steps to do this are the following:
1. Open the level manager and change symbology to override.
2. Select the reference file from the target tree on the left.
3. Change the symbology of the reference file to what you desire.
4. Select the Active file from the target tree.
5. Do a right-click in the level section and select all.
6. Do a right-click in the level section and select properties.
7. Change the color, style and weight for symbology overrides to off.
8. Go to Settings > View Attributes and toggle on Level Symbology.

The levels for the active file will not be affected by the override
symbology but the levels for the reference file will be changed.