In order to get long running queries running in superset moving to the in cluster database is needed. Further description in https://phabricator.wikimedia.org/T340623 Unfortunately the external mysql db is not directly compatible with the internal postgres db. Described in https://phabricator.wikimedia.org/T343526
As such the database move will drop the existing data. However for anything that is of interest, the old instance will be available until 2023-10-16 at: https://old-superset.wmcloud.org/
From there you should be able to login, go to the section with the desired object (Dashboards, charts, datasets, saved queries), mark "Bulk Select" select anything that is desired, then export. On the new superset (available at superset.wmcloud.org starting on 2023-09-11), go to the same section and push the import button (which looks suspiciously like a download button) and import the file that you exported from the old superset.