@m0ltar thank you for providing more clarity about the requirements. Please see below two links that guide you on how to setup QuickSight to access data sources such as Redshift/RDS/S3 setup in another AWS account.
1/ Set up cross-account access from Amazon Quicksight to S3
2/ Amazon QuickSight deployment models for cross-account and cross-Region access to Amazon Redshift and Amazon RDS
3/Use Amazon Athena and Amazon QuickSight in a cross-account environment | AWS Big Data Blog
Let us know if this helps in solving your use case.
Thanks
Deepak