Here’s the dashboard at 2000px
at 2200px
at 2400px
at 2600px
For me, 2000px works well.
You can also see there’s a difference in the left alignment of the text
For the scenes, here’s how it looks at full width
Personally I find it looks big compared to the size of the menu above.
The Duplicate / Delete buttons at the top right and the Start / Save buttons below — it might be better if the bottom buttons were also aligned to the right.
A button to expand the display seems like a good idea