Just wonder what this is (circled in red), can we create thunkable screen sizes by ourselves?
It has Dimensions 1024 x 1366.
Is this feature available to us all?
Or is it something else, something that only this person has?
There are width and height properties that you can use for this, but it would be better to consider a “safe area” to place your app content and leave a generous margin at the edges to account for different aspect ratios.
This is something you have access to in your browser too - if you right click and choose “inspect” if will open the developer console in most browsers.