Blocking the UV elements from moving beyond the UV area boundaries

In most cases, UV elements (vertices, edges, faces, islands) can be freely moved anywhere in the UV Edit area. However, sometimes it is undesirable to move the UV beyond the boundaries of the base UV borders, for example, to ensure that the UV does not "move away" when baking it into atlases.

Read more: https://b3d.interplanety.org/en/blocking-the-uv-elements-from-moving-beyond-the-uv-area-boundaries/