Extrude Manifold
Reference
Mode:
Edit Mode
Tool:
Toolbar ‣ Extrude Manifold
Menu:
Mesh ‣ Extrude ‣ Extrude Manifold
This tool is very similar to Extrude Faces but enables Dissolve Orthogonal Edges by default. This causes the tool to automatically split and remove adjacent faces when extruding inwards.