I've used the Wyeast Sweet Mead yeast and it still went fairly dry. Not like a desert wine. Maybe a percent or two residual sugar. Champagne and Dry Mead yeast will ferment it to high alcohol and very dry.
Sweetness is a function of how much honey and to what extent the yeast can ferment it dry. It's been a while since I brewed much mead, but I think the Sweet Mead yeast did what you want with a mead on the order of 3 pounds of honey per gallon. Remember, you need to add acidity and nutrients.
An alternative would be to ferment with champagne yeast and then arrest the fermentation with sulfites. I think that's how wine makers make sweeter wines (I think?)
Oh don't give me none more of that Old Janx Spirit
No, don't you give me none more of that Old Janx Spirit
For my head will fly, my tongue will lie, my eyes will fry and I may die
Won't you pour me one more of that sinful Old Janx Spirit