I have made a more detailed blog post with examples that can be found here: https://jess-ambers-blog.weebly.com/home/goodnotes-transparency-and-background-colours

As someone who makes GoodNotes journal covers, I appreciate flexibility in being able to make covers that look like real books. Part of that includes rounded corners and things that protrude, like the clasp on a filofax planner. When I make these images as transparent PNGs, the background becomes white in GoodNotes. I've tried to alleviate this by adding a solid grey background, but this isn't good enough for a couple of reasons.
1. The shade of grey is not consistent between the main menu (RGB 230 230 230) and the editor (RGB 193, 193, 193), so one file simply wont look good both ways
2. If I upload the files for sale, I'd have to make multiple versions with transparent, lt grey and dk grey, to suit all possible scenarios. This takes longer to make, its a lot of files to ask someone to download, ect.

In addition to this request, it would be good if the border that appears around notebook covers and pages, both in the main menu and the editor, could be enabled or disabled. This would also help non-perfect-rectangle notebook covers look more realistic.