This all secret/commands were good to work with 2000+ versions of Auto-cad.
1.)TRIM AND EXTENDED DIMENSIONS:-
Trim and extend commands were common commands for all people who were working on auto-cad,this is such a handy feature and it seems that most user don't even know they can do this.
Use either Trim or Extend command to modify dimensions as well as arc, lines etc.
2.)TRIM YOUR HATCHES:-
The new hatch capabilities allow you to trim your hatches just like you would other objects.