planes not remaining highlighted doing functions


Hello;

      I'm trying to remember how to resolve this issue; when like going to do a mate, you hover over a plane in the design tree, but it only highlights

for tenths of a second in the model area, then it's gone. This might give you a guess, but often I'm not able to see which is which etc. I believe there's a setting or something where you can get the planes to stay highlighted. Does anyone know what the setting is for that?

Thanks, in advance for any input;

Rob_D SW 2015_Sp5

SolidworksAssemblies