No. In ArcGIS Dashboards, it is not possible to enable or disable expansion for specific dashboard elements. The 'Allow element expansion' option is applied to all dashboard elements. Follow the steps below to change the 'Allow element expansion' option in a dashboard.
A dashboard can be also be customized by moving, resizing, tabbing, and grouping the dashboard elements. Refer to ArcGIS Dashboards: Dashboard layout for more information.