How to import Credit Memo and Vendor Credit into QBO

You need to use an importer tool

https://get.transactionpro.com/qbo

It's good to have you back here in the Community, Ivan.

Let me add some insights. 

I agree with what @Fiat Lux - ASIA said. Moreover, you can look for a third-party app in the  App section. Here's how:

1. Go to Apps.
2. Select Find apps.
3. In the Search field. Enter a brief description of the app you're looking for.
   
   

This link also will help you find the app that you need: https://quickbooks.intuit.com/app/apps/home/

Feel free to route back here if you have additional questions. We'll be happy to lend a hand. Take care, and have a good one!