I think Yamato could be Robin's personal body guard.
Some people are saying that Yamato could be the log keeper, but Nami is already doing that. Plus Yamato log keeping isn't gonna be that useful imo when she's starting from well into the New World and the story is already well past the half way point.
I vouch Yamato to be the crew and Robin's body guard. If the WG are serious about kidnapping Robin from the crew since Luffy is already so close to the One Piece after defeating Kaido and getting the Road Poneglyphs, then narratively it should make sense to have the WG sending out more agents like CP0 to go after Robin.
Robin would be most vulnerable when she's away from the Monster Trio and the rest of crew, like when she's going out shopping with Nami, taking a bath in the public hot springs or going alone to read Poneglyphs in some ancient ruins. Yamato can be her personal body guard following her around and watching her back.
This would be fitting for Yamato as it puts her strength to good use, something that she already did during the Wano Arc i.e protecting Momo and freezing the bombs. And it also gives yamato the perfect chance to explore and see the world, as Robin is good with directions and likes to explore unknown places. It should help satisfy Yamato's curiosity and she wouldn't get lost with Robin, unlike if she were to follow Luffy or Zoro all the time.
Yamato can also enjoy coffee and shopping trips together with Robin and Nami, you know things that a young lady like herself should be experiencing.