With a few exceptions, ShareGate Migrate preserves unique IDs for all taxonomy objects (term groups, term sets, and terms) in SharePoint.
ShareGate Migrate is not able to preserve your managed metadata IDs in the following scenarios:
You migrate a taxonomy object within the same term store.
An object with the same ID exists at the destination.
Your destination is a SharePoint 2010 server (it is not supported in that version).
Most exceptions exist because a term store cannot have multiple objects with the same unique identifier or ID.
In these cases, ShareGate Migrate generates a new ID and shows you a warning in your migration report.
There are no warnings in your migration report with a SharePoint 2010 destination since it is not supported.
Tip: ShareGate Migrate can preserve your IDs if you migrate taxonomy objects to a different term store in the same environment.