The pop up is not re-sizable in Operation Dashboard.
@AzinSharaf I am marking this as 'already offered' in the sense that things are working as designed/intended. The Details element shows a layer's popups. In cases where a map is too small to show a good popup, or the popup's content is too 'robust', a Details element (which can be resized) is provided as the alternative as it can be re-sized as needed.
In ArcGIS Dashboards Beta, the popup has been improved. It is more responsive to the popup's content and/or the map element's size.
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