...yeah its in the tool options, have a play with the options...

maintain position is used to determine if the edge loop will be inserted in the center or relative and how many edge loops you want

just have a play

i've never used mj polytools before (or i might have but i didn't see the point in having it since it didn't do anything new)
if it's what i'm thinking of then all it does is put the shelfs with the buttons up top into another window. anything it can do you can do with the tools on the shelf as they're the same.

i might be wrong though.. there might be some special tool that does something that requires more than a few clicks if you did it normally