WARNING : In order to be able to update similar products across multiple store using this tutorial, SKU must be already associated with all the related products and options. If the SKU is not available on all stores for similar product, this process will result with duplicates.
On the Back Office : Exporting updated products and options from the souce store
Go to the source store Back Office Product Page and click Export CSV
Name the CSV after the store name
On Excel : preparing the Import CSV for the target store
Open the CSV on Excel
Delete the ProductId column except for the header
Delete the rows of products and options you don't want to update
For the remaining rows make sure that the SKU is populated and already added in the target stores.
Export the tab in CSV with semicolon as separator
On the Back Office : adding products and options with SKU in the new store
For each target store :
Go to the store Back Office Product Page and click Import CSV
Select the generated CSV
Click OK
The store products and options are duplicated with SKU