3.3.1 Loop cut and Extrude Manifold
A powerful option introduced with Blender 2.9 is the Extrude Manifold
that can erase and split faces based on extrudes. It works better for
extrudes made to the interior of a model. You can see the real benefit of
such extrude mode when pairing it with a Loop cut.
To see the benefits of such extrude, we can take an example from a
simple cube that receives a horizontal segment with the Loop cut (Figure
3.13).
Figure 3.13 - Cube with single cut
In Figure 3.13, you can see a selected face where we apply both an
Extrude Region and Manifold. The results are shown in Figure 3.14.