Update for the increased Inventory Size.
Still lazy to switch to a new UI even though I do have to do it at some point in time. So here's an update to the new Inventory Size of 50.
Replace <Vanguard Base>\VGUIAssets\Shells\ManicUI\Windows\ManicUI-Inventory.xml with this.
Many thanks to Whaught Naught of Seradon for the quick tips saving me a few hours of research.