I can't find how to toggle between timeline and list view OR how to find the summary.
We went into Managed Saved Views then back to plan and the left menu shows with the choices and the timeline/list options (old view).
You can also add "timeline" back into the URL path and it will the list option again
.../scenarios/10/timeline?xxx
There is an active incident for this, see https://jira-software.status.atlassian.com/incidents/lb04yjdct854