You can simply turn off the Sketch Geometry layer from the pull-down list if there is no other sketch geometry you are interested in.
If there is other sketch geometry(or just part of the sketch geomtry) that you wish to retain - turn off the Visible (and other layers like Hidden as appropriate) to make it easy to select the sketch geometry. Then window or crossing window select the sketch geometry you wish to hide and right click - Hide. Then you can turn the other layers back on.
This is a really powerful trick where you have an huge number of hidden lines - so many that they obscure the presentation of design intent, but you want to keep some critical hidden lines.