At the moment, it is possible to manage the dashboards in your Jira instance by going to the Cogwheel at the top > System > Shared items > Dashboards.

Reference: https://support.atlassian.com/jira-cloud-administration/docs/manage-shared-dashboards/

But there is not an option to automate or make changes in bulk to the dashboards, you have to go through each of the dashboards and manage them individually.

Suggestion: Provide a way to perform these changes in bulk such as via REST API.