Hi Sandbar
I've already read your messages and saw your screenshots but these screenshots have nothing to do with Multi-Inventory.
Perhaps there is a misunderstanding of how Multi-Inventory works. Please check how a product with multiple inventories looks in Stock Central:

And each inventory has its own location (the blue marker icon).
And If you reread my messages, I've said:
There is a split inventory functionality. But apart from this, you can adjust the stock for any inventory manually at any time (from Stock Central or from the product pages)
I'd recommend you read the Multi-Inventory documentation:
https://stockmanagementlabs.crunch.help/en/atum-multi-inventory
If you have further questions, please let me know.
Best Regards,
Salva.