I've come across a visual glitch that happens in the tool bar when Pixelmator Pro 2.0 is in light mode, fullscreen and has only one doc open.
Big Sur 11.0.1
iMac (Retina 4K, 21.5", 2019)
3GHz Intel Core i5, 6 cores
Radeon Pro 560X 4 GB
(I'll probably use Pixelmator always in dark mode from now on anyways, because 2.0 light mode is awfully uglier than 1.8's: 2.0 is full of boxes, bars, separations, light and medium gray areas where 1.8 felt sleek and integrated. Thankfully dark mode somewhat conceals it.)
Is something not working like it should? Let us know.