Researchers doing glycoproteomics using Skyline have a need to define charged losses from specific modifications, the way we currently allow neutral losses from structural modifications on peptides.

Here is a relevant support request:
https://skyline.ms/announcements/home/support/thread.view?rowId=41072

It has also been requested that we support some existing lists of glycan structure modifications found in human samples. e.g.

https://assets.thermofisher.com/TFS-Assets/CMD/manuals/man-xcali-97974-biopharma-finder-user-manxcali97974-en.pdf#page=559

It seems like we are likely to want to define charged losses from these structures, though it is not yet immediately obvious from the above list how we would get that information.

Charged losses were implemented on November 5, 2019:
https://github.com/ProteoWizard/pwiz/pull/692