This is what I tried to do with my system. Sorry for the poor image quality but all I have handy is a cell phone camera. These are Leviton Decora style inserts with keystone connectors.
The 5th insert from the top left (the big black circle) is a toslink insert. Bad news is it is not working. I am using Blue Jeans Cable optical cables. I can get a 4ft cable - insert - 4ft cable to work. But a 4ft cable - insert - 9ft cable will not work. I am not sure if the ends are not finished properly that cause too much attenuation in the insert or if the plastic cables just have too much signal loss. I have thought about using quartz cables with polished ends to see if it fixes the problem but I am not sure how much money I want to throw at this trying to fix it. The safest bet is to go with the above mentioned multi-cable wall plate and use a single optical cable.
Good Luck.
