By default Intent Manager is on when sketching. Use the config.pro option sketcher_intent_manager set to no if you want to start the sketcher without Intent Manager turned on.
For those users who are more familiar with the old sketcher-Intent Manager can be overwhelming. You have to change the way you sketch from start to finish, but in my opinion Intent Manager saves plenty of time. (Intent Manager on - define dimensional references first, sketch, constrain/dimension; Intent Manager off - sketch, trim entities, align entities, dimension, regen.)
I have used both methods for sketching and Intent Manager is far better than the old method.
If you like some of the Intent Manager functionality I would suggest that you do not highlight the entities, (vertices, lines, arcs, etc.) so that they are not changed.
If you are clumsy with mouse picks then try locking the dimensions that you do not want Intent Manager to modify.
Lock a dimension - pick/box the dimensions 2) Select "Toggle Lock" in the Edit menu.
The selected dimensions are now locked and can only be changed by modifying their corresponding values. (Try moving the lines or vertices) Intent Manager will not adjust the dimensions when locked.
Notice that all locked dimensions will have the letter "L" adjacent to their value. Also, locking a dimension in the sketcher mode is only valid for that particular sketch. Once you exit the sketch (the check mark button) the locks are removed from the dimensions.
Have fun!