A body’s object type is stored as ECC_GameTraceChannelN, a position in the channel list. The name you gave the channel lives only in DefaultEngine.ini. So inserting, deleting or reordering a custom channel leaves every asset holding its old slot number, which now means a different channel. Responses are stored by name and survive, which is why forum threads disagree about whether channel order matters.
CollisionChannelRedirects handles renames only.
Collision Channel Migrator is an editor commandlet. Snapshot records which name sat in which slot; commit it. After the change, Plan writes a report and changes nothing, and Apply rewrites and saves. Bodies driven by a named profile are left alone, and a deleted channel is reported, never guessed.
UE 5.8, Win64. The code is AI generated. $14.99 on itch, or $10.49 in the UE5 Rename and Migration Safety Tools sale until 12 October 03:00 UTC.