How to Increase Inventory Slots in Dune Awakening
How to get more Dune inventory slots? Well, that's pretty simple at this point, you can't. No feature in the game allows increasing Dune inventory size or expanding personal carrying capacity. This is done on purpose to make players think carefully about what they carry and how they manage their resources.
Can more inventory slots be added?

Make Your Own game Server
This is currently not possible in Dune Awakening, and it won't be. By design, core survival and resource management are parts of the game, and there are default limits to the slots within that.
Alternative Methods of Inventory Control
Since there's no direct Dune inventory slot increase, here are ways to handle your items more effectively:
Use storage and vehicle containers

Conserve your precious personal inventory spaces with the help of storage chests, base containers, and vehicle storage. Unload heavy resources; keep only the things you would use right away.
Split heavy items, if necessary

If ore, stone, or whatever the material obstructs you - quickly make separate stacks and discard excess piles in the world for some time; this is helpful in emergent situations where agility is everything.