You can trim, extend or split/segment elements with buttons on the Draw toolbar. You can also add fillets or chamfers by clicking Fillet or Chamfer on the Draw toolbar.
Relationships are added or removed as necessary when you trim or extend an element. For example, if you trim part of a circle and more than one arc remains, concentric and equal relationships are applied between the remaining arcs.
You can also draw a chamfer on two different elements with Chamfer on the Draw toolbar. The elements must be linear, but do not have to intersect. The elements cannot be parallel to each other.
When two lines intersect, you can draw a chamfer simply by clicking the corner and then moving the pointer in the distance that you want. A final click on the drawing sheet places the chamfer (B).
To place a fillet, you can click Fillet on the Draw toolbar and then select the elements you want to modify. As with any command, you can use a combination of clicks and ribbon input.