When I right click on a contributed explorer sash, i get a context menu to Hide it:

To unhide it, i have to know to right click on the EXPLORER area at the top of the viewlet, and then I get a nice list that I can toggle things on/off:

This suggestion is to show the entire context menu on the right click of any explorer sash, instead of the "Hide" context menu. This would give me as the user an indication that i can toggle explorers on/off as soon as i find the context menu.