When I add more than one metric in Vital Signs, I would like the URL to be updated to include that metric too, and distinguish which one is presently visible.

for example:
https://metrics.wmflabs.org/static/public/dash/#projects=enwiki,frwiki/metrics=RollingSurvivingNewActiveEditor,[RollingActiveEditor],NewlyRegistered

the square brackets denote which is the visible metric when the page loads.