If so, what I would try doing is create another split animation in the inspector for example in the middle of a Jump.
Say the original jump goes from frame 100 to 200 use the Animation Editor Unity has to see which frame you want to be frozen say 156 then create a new split animation Called JumpStill (Start 156 End 156) then Call and loop that animation for the time you need.
This is TOTALLY just a GUESS but its something that I might try if I wanted the character to be frozen. And there is probably a proper or better way to go about something like this but this is what I would try meaning my guess.