Q - Level import into DGNLIB via csv file

I'm trying to clean up my dgnlib with about 350 levels. I exported it into csv file, loaded into Excel, made changes, added few new levels and deleted some I don't need. once finished, saved file to csv again. when I try to import it into clean DGN file there is a message "Unable to find level library". I'm using SS4 with no project, no user, no workspace configuration so I don't know what library is meant here.

when I check new CSV file against original one it looks identical (I mean, the format of file). is there a working workflow how to simply edit lots of levels in Excel and import it in DGN?