List on Amazon / eBay only - not web store
It is possible to add a product to Magento but have it listed only on eBay, not on the website.
On the General tab of Product Information of the Catalogue Item:
Set Status to Enabled
Set Visibility to Not Visible Individually
Publish the Listing
Find the product in XpressGrid (Marketplaces | Codisto > Manage Listings), set your options (Amazon or eBay tab) and set Amazon Status / eBay Status to Enabled.
Finally push the save button in the XpressGrid Header