You have the possibility of transferring ongoing sales without bids to the seller account you wish to keep, thanks to Store Plus.
You can then import them into the main account using the Easy Uploader tool.

To successfully transfer sales, all the accounts concerned must have a Store Plus membership.

This article covers the following topics:

To subscribe to Store Plus

To subscribe to Store Plus, please read the article "Store Plus Service".

To export sales from the "secondary" account

You can export your ongoing sales in "Lister / Easy Uploader" format (it is important to export in this format).
This article explains how to proceed: How do I export my sales?

Warning: the exported file remains valid for 3 months. After that, the links to the images will expire.

To import sales to the "main" account

You can import the sales file previously obtained by using Easy Uploader.
This article explains how to proceed: Listing your items with EasyUploader