Berries are nutritious. Now this fact can be realized in Timberborn with the help of this mod.
This mod adds a nutrition need for berries. This has the important effect of making beavers actually want to eat the berries in storage.
Naturally, this makes berries also provide +1 well-being. However they are a pretty seasonal food (12 days to grow 3 berries) and don't provide any other bonuses so it does not upset balance in any way.
Copy the mod folder into your BepInEx/plugins directory.