Hello,
I use multiple profiles, one per character with different priorities (1, 2, 3). But with the new patches, the new mounts are added automatically on priority 1.

Can you set a new priority for mounts in future patches to "Undefined" instead (equivalent to disable) ?

There is a setting for this on the General tab, "Automatically disable newly added mounts."

If you tick that box new mounts Blizzard add to the game will have priority 0 instead of 1.

Thank you.