The notebook editor is a virtualized list view rendered in two contexts (mainframe and webview/iframe). It's on top of the builtin list/tree view renderer but its experience is different from traditional list views like File Explorer and Settings Editor. Making the notebook cell list view work with good performance and smooth scrolling is not trivial, most of our improvements are tracked in the doc. The following sections here can help you to report layout issues.
Replay is an app/browser which can capture browser sessions, including DOM, user interactions and network events, and generate a recording which can be used for "time-travel" troubleshooting.