Path-cutting mesh.

[Gayngel]

I need to resize some meshes with llSetScale() but I only want to resize one side of the mesh. Is there way to do a path cut in Blender?

[Coffee Pancake]

A single mesh object (made from a single mesh part) can only be scaled the same as prims.

If you need to rescale part of a mesh, that part needs to be a separate mesh

[Wulfie Reanimator]

You can achieve the same effect as path-cut prims by expanding the mesh on one side, so that the bounding box' center is on the edge of the visible mesh object.

Basically this, note the extra plane on the left side.

You don't need to set the origin, but setting it to geometry helps you check if you've done it correctly.

You also don't need to use an entire quad, and even if you do, you should scale it down to infinitely flat (0) on one side so that it doesn't show in-world.