How do you inset faces in a certain direction?

I’ve been working on a Blender low-poly character tutorial from Imphenzia where I model the Mandalorian, but I don’t know how to inset some faces to the left, towards the mirrored half of the model. How do I do that?

You mean this?

press I and then B (for Boundary)

Inset operator (or tool) has a toggle for mesh boundaries, hit B while insetting