Hi there,
I'm assuming you mean the gene selection window which disappears when you click on the << (circled in red)

If so, you can bring it back by clicking on the left-hand border

If this is not what you mean, post a screenshot, and I'll see what I can do to get you back to default.
best wishes,
ginger
On Wednesday, October 26, 2016 at 9:15:14 PM UTC-7