8.2.1 cannot record BFA alchemy transmute cooldowns.
It can record tailoring cooldowns, but alchemy.

After enabled debug mode. for xmute
First, Clearing Trade skill cd
Second, Trade skill cd

Set all BfA Alchemy spells to new type, different from "xmute".

UNIT_SPELLCAST_SUCCEEDED is not fired when open tradeskill window for scanning.

Sorry for the delayed reply.

I found two things in recent research, the first is BFA alchemy transmute will let LEG alchemy in cooldown as well, which is not in previous expansion. The second is we didn't update the code for UNIT_SPELLCAST_SUCCEEDED, so it's not working now and cannot tell the different between the trade skills which are sharing cooldown. I think fixing the latter one can fix this issue either, but adding new type is not helpful. Different types only control the display name of trade skills.

it is fired when player casts trade skill, so SI can record the correct one than taking a full scan and getting confused by a list of spells sharing cooldown.

Yes, you are right, that's one bug.
It can't fix cooldown scan when open tradeskill window, that's another bug.
There are 2 bugs on SI.

It won't record the missing BFA alchemy transmute cooldowns actually.

How to repeat:

1. Cast BFA alchemy transmute, SI recorded. you fixed the bug at commit f594e63.
2. Log out, and wipe SavedVariables\SavedInstances.lua.
3. Log in. Now, no BFA alchemy transmute cooldowns list in SI.
4. Open alchemy skill window, the BFA alchemy transmute cooldowns is still missing in SI.
5. Like the post 2 and 3, new type needed.

I think it is being fired by TRADE_SKILL_LIST_UPDATE and triggering functions.

It's because BFA alchemy transmute shares cooldown with LEG's, so SI is confused by them and choose LEG to display.

Ok, I found the problem.
I havn't learned LEG Transmute except Transmute: Wild Transmutation.