Didn't find any way to merge 2-3 dashboards into a main one or copy object from one to other.
DX UIM 23.4.X
Product limitation.
The Dashboard Designer does not support merging one or more dashboards into one, nor does it allow copying widgets from one dashboard to another.
However, we can link one dashboard to a widget in another dashboard.
If you consider this option important for your business, create an enhancement request so that this can be reviewed by the product management team for future releases.