You can display and edit multiple UV coordinate sets simultaneously in the texture editor. These UV coordinate sets can belong
to a single object, or, if more than one object is selected, to multiple objects.
This is useful for a number of tasks including:
Positioning one object's UV coordinates relative to those of another object on the same texture image.
Positioning multiple UV coordinate sets belonging to a single object on the same texture image.
Making sure that geometrically identical objects' UV coordinates are unfolded the same way.
Creating a single set of rendermap images for multiple objects, as described in Generating a Single Set of Rendermap Images for Multiple Objects.
You can select and modify sample points on multiple coordinate sets simultaneously. You can snap sample points from one set
to another, and copy and paste coordinates between sets. However, the different coordinate sets are independent for the purposes
of operations like healing, relaxing, and matching.
To display and edit multiple UV sets
Select multiple objects or an object with multiple UV sets, and open the texture editor.
If the texture editor is already open and locked, click Update after selecting the desired objects.
On the menu:
Click on a single UV coordinate set to isolate it for display and editing.
Shift+click to toggle one or more UV coordinate sets for both display and editing.
Ctrl+click to toggle one or more UV coordinate sets for display but not editing. For example, this lets you snap UV coordinates
from one set onto another set without accidentally selecting and modifying the second set.