If there is a product that you do not want to sell in your Magento store, but you want to list it on the Channel via M2E Pro, edit certain Product data in Magento first.

Just follow the given instructions for Magento 1 and Magento 2:

Magento 1:

Navigate to Catalog > Manage Products and click on the relevant Product in the grid. Open the General tab, set Enabled in the Status field and Not Visible Individually in the Visibility field. Click Save to confirm the changes.

Magento 2:

Navigate to Catalog > Products and click on the relevant Product in the grid. Set the Enable Product option to Yes, and select Not Visible Individually in the Visibility field. To confirm the changes, click Save.

That's it! Now the product will not be visible in the Magento store but can be listed on the Channel using M2E Pro. Channel orders for such products will be imported.