How to Increase Satchel Inventory Size - Pokémon Legends: Arceus
To acquire more satchel slots, you must complete the "Summoned by commander Kammado" mission.
After you leave the Galaxy hall, Bagin approaches you and offers to teach you how to expand your inventory.
In order to upgrade your Satchel, you'll need to speak to Bagin, who can be found standing beside the left stairway of the Galaxy Hall building in Jubilife.
When you need more space, go see bagin.
Upgrading your satchel will give you one extra slot in your inventory space, which is useful when you are crafting.
The first upgrade is P100 and every slot expansion will cost more.