How can we enable a calculated metric in multiple report suites at a time ?

calculated metrics can be shared at user level

https://experienceleague.adobe.com/docs/analytics/components/calculated-metrics/calcmetric-workflow/cm-sharing.html?lang=en

If user has access to report suite then should be able to see it shared. 1 caveat if report suite does not have the base key dimension of a calculated metric sharing it may not work.(never tried it)