Variable Mods for glycopeptides

[ABB-808]

Hi-

I've been using the fragpipe N-Glyco-HCD/LFQ and O-Glyco-HCD workflows for glycopeptide analysis. Some of my protocols involve chemical modifications to terminal glycans. I am wondering if there is a way to add a variable modification to a glycan in these workflows. I believe the only way seems to be manually changing the mass offsets of the glycans to represent the chemically modified glycan. I've tried open search too, but that does not yield any results.

Is there any way to create a variable mod for glycans? If not, is there any other method supported aside from adding all possible mass offsets?