@jimcullen Expand on hover for the sidebar has been in release for a while now - since 138. You need to click on the gear icon in the sidebar to open the "Customize sidebar" panel and select "Expand on hover".
Hi, there's a few issues with having the rounded corner in the content area that we're working through with the platform team (that's one of the issues) and it will unfortunately take time to fix. The rounded corner is on by default only in Nightly, ...