system options featuremanager sketches

You could use the search bubble at the top of the FM and type the word "sketch" or whatever you may have renamed the sketch to be.  It acts like a filter to show all the items that contain the keyword you use.  Then just select the items you wish to hide / show, CRTL select works here for multiple items.  When you are done click the X in the corner of the bubble and your FM will go back to normal.

Regards,

David O.

Always a good idea to rename your sketches and features in order to use the filter as per David's advice. Also, you can use the Go To... command.