how do I connect a category to a transfer from account to account?

Hello,

There is no way to add category to transfer. 

Accounts are your wallet or bank account, etc. You can move money between them, but this will be not expense, that you are doing using categories. 

You can make transfer to another account and then make expense in it. Or you can write description in transfer notes.

For example: 

You need to transfer money from your Debit card to your Wallet. In this case you make transfer from Debit card to Wallet. 
Or if you need to transfer money to Credit for your new car. In this case you need to transfer money from your Account 1 to Credit account.You can see that you owe less now to your Credit account.

I hd a feeling it wasn't possible... Thank you for your reply! :) It would have made things a lot easier to see the actual amount under expenses that you use for credit cards and also see the new balance of the credits after a bank transfer.

I hd a feeling it wasn't possible... Thank you for your reply! :)