It is best practice to manage dgnlib files outside the day to day working environment partly to avoid unwanted duplication of levels and other library content. One method is by using an administrator User Configuration file containing appropriate variables.
If you are the CAD/BIM administrator, copy your existing <name>.ucf file to Admin_<name>.ucf, then using Notepad++ or a similar editor add the variable:
BB_DVDATASETELEMENTS = 0
This will disable the copying of dataset library levels into the dgnlib when you are working on it.
Another approach is to work on dgnlib files in MicroStation if it is available.
AECOsim Building Designer copies levels and linestyles needed for Dynamic View creation into each file on open. These are required for DV operations but are neither needed or wanted in dgnlibs other than the source dgnlibs in the dataset.
Unwanted content can be compressed out of dgnlib files by careful use of the Compress Options or the key-in "delete unused" with options as appropriate, eg "delete unused linestyles".
Obviously you should not use this example command in a dgnlib that actually contains your library linestyles!
Search help using the string "delete unused" for all options for the 'delete unused' key-in.
A series of key-ins can be appleid to a whole set of dgnlibs using the Batch Processor. An example of using the Batch Processor is described in Batch Update of Cached Visible Edges (CVE) in AECOsim Building Designer.
Mstn should automatically set this when a user enters a dgnlib....