Extruding inwards without creating double faces I'm trying to extrude the selected face in Cube #1 by pressing E, left click then move along X axis. The desired result is Cube #3 but what I get is Cube #2. Is there any workaround for this as it seems a very simple problem and I find it weird that this function hasn't been implemented yet.
Thank you in advance!
Press Alt + E and select Extrude Manifold.  Blender will move all the edges of your selection back while creating a new face under the lip, just like you want.