I want to give some feedback for the current state of the controller implementation and UI in Patch 5 on Stadia.
1. Tooltips and missing content which is available on PC
On PC this is easy because you just need to hover with a freely movable cursor. With controller you have no cursor and cannot hover. The current implementation is to use L3 to show or hide tooltips. Personally I like that. But it's still very buggy at the moment and many things available for PC are not implemented yet on controller or were simply forgotten
=> Many tooltips which are available on PC are not shown if you use a controller. Please add them or make them available.
=> It is not consistent. Since tooltips are a very important aspect of the game which are needed almost everywhere they should always be activated by using the same button (L3). However for some unknown reason it is Y when being at the merchant screen while L3 is used for sorting or something like that.
=> When being on Charactersheet and trying to get tooltips it sometimes works but then it doesn't on the next entry. You have to hide tooltips then move a few entries go back and then press L3 again. Definetely a bug.
=> Tooltips are missing on new abilites like the Battle Master feats during character creation and level up so you don't know exactly what they are doing if you don't know DnD5e => That's important!
=> You cannot toogle some checkboxes like show only "hair that fits race" during character creation
=> You cannot hide/show helmet
=> Tooltips on dialog checks work only once, not on the second check. Again this is a bug because the first time it works well.
=> If you examine an enemy you cannot scroll down the information.
2. Battle and movement system
=> There is no way to control multiple characters of your party (at least none that I know of). I am missing especially an option to let everyone hide (move to stealth mode) at once. Currently I have to select Hide for every character and press L2 to select the next party member which is very tedious.
=> If you choose an ability (like a spell) and your cursor is above an enemy you do not select that ability. You have to move the cursor away from the target, select the ability and then aim at the target. Again this is a bug.
3. Inventory Management
=> Add an option to select multiple items like Ctrl+Left click on PC and with controller something like hold X for a specific time to enable select mode and then you can select by pressing A. The you can press X to open menu and for example send all selected items to camp instead of doing it for every single item. On mobile phones it is usually the same to select multiple entries: Long touch to enable select mode and simple touch to select or deselect. You can use the same for controller and since the people know it from their mobile phones it is intuitive.
4. Loot
Looting every single barrel on PC is already a chore but with controller on Stadia it's maddening. Especially since you have to press L1 or R1 in the hope you are facing your barrel or book shelf in the right direction so it is on the list.
Simple fix: Group containers of same type which are all reachable, unlocked and assigned to the same character (for the purpose of stealing) together when it comes to loot. For destruction or movement you can still handle each container as an instance but when you are looting open a menu that shows the content of all barels in that group.
There is already the option to show all interactable or lootable items not in a container by holding A. Add something like that maybe by holding Y that opens a virtual container that has all the lootable and reachable items in that selection. Then you can loot them from that container.
These two things would improve looting tremendously.
All in all I am satisfied with the current state of the UI. You just have to fix the controls and add a few conveniance functions. It should not be that much of work. Please do not put it too low in priority list.