I've been running the Simulator on my high DPI laptop screen at 125% scaling, as well as on 4K monitors at 150% scaling, and I'm noticing that while the Simulator itself seems to respect those scaling values, the gameplay window doesn't, always displaying it at 1:1 pixel values (or 2:1 when using 2X view mode).
This might be by design, to ensure that the gameplay window is pixel accurate, but it's a little strange because on a very high DPI display, even the 2X setting can be a little too small to view when testing/debugging.
On top of that it's a little distracting when using the Simulator in multiple contexts because it often appears a little differently than I expect.
If scaling the gameplay window arbitrarily raises legibility/accuracy concerns, perhaps a temporary solution would be to include a 3X and 4X view mode?
Interestingly, the gameplay window is high DPI aware, you just have to trick it... Since the gameplay window only sizes itself upon launch, if you change your display scaling while the Simulator is open, the gameplay window will scale to the new value.
This screenshot was taken by setting the display scaling to 300%, launching the Simulator, then changing the scaling to 125%.