I should have looked closer. I see now that there is no dedicated FX return jack. Bummer. Has to go back to a channel. Well I guess that means you will only be adding your external FX to the channels you route it back to and that's a good thing. (If it doesn't cause a feedback loop.) But even then it won't parallel with the internal FX either. So that's kind of a bummer again.
BTW, did you see anywhere that tapping the FX send will shut off the internal FX? I think that would be a best situation but I did not find that as I glanced through the manual so I assume either I missed it, they left it out of the manual, or, it will actually allow you to blend the two with the FX To Main knob. Assuming that is "Internal FX To Main" only since there is no dedicated FX Return. That would make sense, I guess.
Anyway, It looks like a decent little mixer. I sort of keep my eyes out for a replacement mixer. I've been using a Yamaha MG124cx as my desk top playback/control room and all-round utility mixer for a good 10 years or longer. Lots of use and no failures but you never know. It sits vertical on a folding guitar stand to the left of my screen. Takes up a lot of space and I never use any where near all the channels. But, it does have all the routing functions I need and use. I figure I'll downsize if it ever goes bad beyond a reasonable DeoxIT clean up.

Does the noise in your head bother me ?