The way to use multiple eBay accounts with Chrome is to create multiple Chrome users for each eBay account.
Click on your user and then "Manage people":
Then click "Add person":
Give it a name and click Add.
Make sure you install SmartyDrop and the other needed extensions for each user you create.
Now in order to switch eBay accounts, all you need to do is change your Chrome user and everything will be ready to go.