In ViewLibraryDlg.InitializePeptides() there's a comment "Don't do this for peptides until we have performance issues worked out", but with the feature finding work, large small molecule libraries are common so the bottleneck reappears. And, ion mobility for peptides is increasingly common so this needs fixing anyway.

It seems to be spending a lot of time in Model.Lib.BiblioSpecLiteLibrary.GetRedundantSpectra - and a lot of that deciding which columns to use to pull ion mobility information. We should be able to cache the detected columns information, and also short circuit the whole thing by checking for ion mobilty type == 0.

This is fixed in the Feature Finding branch