Keefe likes to change his lines often so I don't think his answer would be meaningful tbh. He's a very active coach, will bring different guys in and change around the bottom / top 6 weekly. Either you love that or hate that haha.
Last season he played Nylander at center in pre-season / first several games, at LW, and at RW. He played Marner on RD several games when there were injuries. He had Tavares / Nylander running the third line individually at times and other times had them mixed up in the top 6. He played Tavares at LW as well, played Domi everywhere from 3rd line C to top line winger, etc.