Super 10 speed popping out of gear

I would be looking at the shifter itself and shifter seat first. Since there's is no grinding. It's possible that the bushings are worn where the shifter goes in the top of the transmission

 

When mine did that the gear was worn so it slipped out sometimes. The tranny eventually was replaced. You can pull the fill cap and see if its magnetized check for an accumulation of metal particles. That doesnt fix nothing but it'll give you something to think about, as long as your at it you can check your fluid levels, & top it off.
As long as its still working for the most part keep on trucking with it.

 

There is also a possibility that the shifter fork is worn along with the sliding clutch on the main shaft. If you get it looked at now it may be a fairy inexpensive fix.

 

Hmm, lets get past the terminology barrier. Now describe it as in movements. So, you have the shift lever all the way to the passenger side, then to the rear, with the splitter (grey) forward. Then as you drive, or how long, when you apply throttle (torque), the shift lever "pops" forward on its own. Then as you let off the throttle, the shift lever "pops" or slides backwards into the correct position. Is that what you are talking about?

 

If it's slipping your clutch may need adjusting or even be shot but from what you describe I'm not sure if it is slipping? The lever comes out of the hole?