1. I have recently came across the issue that user can't use "Show All" option when picking Products for Order in Admin. It's on top-left corner and there are two options in total, but there is no change if I select "Show All" while it should show me the list of all Products without the structure.
2. Other thing on the same screen, but this might be something on my end. I still think to report it here so you can look if it's repeating on your end. When I try to change the Columns that are shown on the same page (product selected), on save page refreshes, but now I can see more buttons which are actually below to Catalog toolbar (ie. Add Product).
Anyone else can test these in 5.1.0-RC1 and confirm?