You can keep the Layer and Page Gallery open all the time by pushing the little pushpin in the upper right corner of the gallery once it is unfolded. (If you hover over it it will show a pop-up with the text "auto hide") If you want to keep it open the pushpin should be in upright position. You can even drag it from the border of the window and drag and size it to a place where it won't be in the way.

Hope this helps.