Cut, Extrude, Bevel

Cutting edges ... knife subdivide ...

Select some edges or a face ...

Shift K

Midpoints

Drag a line

Enter to accept

(esc to cancel)

The cut is made at the midpoint of the affected edges

Plus, other edges are added as need to ensure the mesh remains with only 3 or 4 sided faces.

Exact line

The same process, but Blender is not concerned with midpoints

 

 

Multicut

You can delete and edge loop

Edge arrived at by converting a face to triangles

Edge flipped by rotation

  

If you have a “hole” you want to fill ... select the edges

Bevel

 

Ctrl, to scale in 0.1 steps

Shift to scale in 0.001 steps

Enter a scaling value by pressing Space. A popup dialog appears, , asking you to type in the beveling scale factor labeled as "Width”.

If you want to bevel only one face, you need to use a script: