Leaderboard

If using KTool then go to Tools -> Options -> Other and tick the box to have it check the Override folder for 2DAs. It will show your custom added row in the drop-down list then (may need to be closed and restarted). If using KGFF, look in the PropertiesList and find the property struct with the PropertyName value of 59 (Disguise property's row ID in itemprops.2da). The Subtype value is the appearance.2da row ID (would be 351 in your pictured example).

You're looking at the unpatched UTI by the looks. If you install the mod, or just look at changes.ini you'll see that it adds a custom appearance row with N_CassusFettB01 as the racetex and patches the UTI to point to that. But yes, your summary at the end there is correct.

The basic approach for a full body appearance like this is to set the UTI up as a disguise. It's the same way the space suit, underwater suit, Sith armour, and Sand People clothing works. In the UTI you add the disguise property, which points to an appearance.2da row ID to use as the appearance. In this particular case, the existing Mando rows are set up to use set "racetex" texture overrides (N_Mandalorian01/02/03), so you'll need to create a new row that duplicates one of the existing ones but points to your own custom racetex variant. Since you've already got a mod that does exactly what you want, the best starting point is to poke under its hood and see how it works.

Well there's your problem. I don't think that exists. The MOTF double saber uses variation 7 not 8.