Multiple UV Tiles/UDIMs to one single UV set ?

Question:
I have received from a client a very heavy photogrammetry generated OBJ along with 3 separate 8K texture maps, all on separate UV tiles.
I would like to combine all 3 uv tiles on one single tile, and combine all 3 texture maps one one single 8K map.

Answer:
* This steps only works on the new version 2026.4 *

Once you have the mesh (need to be one mesh) w/udims imported on Paint Room as PPP, with ITAUVset turned ON

On Textures Menu > Import > Import Multiple Udims > select all the images on the folder

All the images are added to Layer Panel

You can modify any uDim texture selecting it on Texture Editor

switch to UV room, and use Unify UV

next step UnWrap

last Apply UV-set

now Delete Unused  UV Sets

Switch back to Paint Room, press OK

Now you have only one Paint Object, one Surface Material and one UVset applied

Done