I have an animation where a character comes walking in the field and then he sits down but the movement between the 2 positions is very brutal. Are there any transitions like in Première that make it possible to smooth out the frame changes?
not unless you create one, or more likely two, (eg, using the bone tool or, less likely for a pedal character, the warp asset tool).
typically you would have a standing and sitting animation and a standing_to_sitting animation (after which the sitting animation would display) and a sitting_to_standing animation (after which the standing animation would play).
typically, the two transitions would not loop and the other two would loop.
In fact I have characters that I animate with the "bones" tool and I go from a symbol character in the standing state to a symbol character in the sitting state. I don't have a transition animation between the 2 states, I just want to put a transition effect, like in Premiere to reduce the change of frame
i'm not sure that makes sense, but if it works for you, then great.