Unfortunately I didn't find anything that clearly explains what these properties should do either:
/p: AzureStorageBlobEndpoint=(STRING)= Azure blob storage endpoint, see SqlPackage for Azure Synapse Analytics.
/p: AzureStorageContainer=(STRING) =Azure blob storage container, see SqlPackage for Azure Synapse Analytics.
/p: AzureStorageKey=(STRING) =Azure storage account key, see SqlPackage for Azure Synapse Analytics.
/p: AzureStorageRootPath=(STRING)= Storage root path within the container. Without this property, the path defaults to servername/databasename/timestamp/. See SqlPackage for Azure Synapse Analytics.
https://docs.microsoft.com/en-us/sql/tools/sqlpackage/sqlpackage-extract?view=sql-server-ver15
Even after filling them in, it didn't result in the process I expected, it wasn't written to storage. I found this property confusing but I didn't find any example of use either...
I'll try to find another way.
Anyway thank you so much for the support astanton1978