All the functions are through using events shown on the InventoryManagerComponent Event Graph. The only function called externally not through an event is “TryToAddItemToInventory”.
You most likely need to know what slot you want to read than you can simply get information from that slot. On the client the client UI is updated with the item info so you can read that data already from the client without having to request it again from the server. Again if you know what slot you want to look up you can read the item data from the client in the InventoryLayout Widgets InventorySlots array. IF you are editing items you will want to use the events in the InventoryManagerController that make changes and they update the clients UI.
Default items are setup in the Blueprints/Demo/ Classes Enum and Classes Starting Items DataTable. This determines the item loadout for the demo example.