To active the tool press SHIFT + CTRL + A and choose Annotate tool.
Delete All = Delete all Sketch strokes.
Delete visible = Delete only visible strokes.
Show/Hide Strokes = Toggle with Hide/Unhide
Angle fallout = smaller number here and quicker stroke will hide from screen.
Show strokes front/back = If you want to see stroke from back and front
Distance fallout = smaller number here and quicker strokes will hide when zooming out.
Overall opacity = Control for all strokes opacity
Apply symmetry = This will apply symmetry when you sketch ether front or top view. Side view is not using symmetry this even if this is turned on.
Strokes per object = You can isolate strokes per selected object.