Hi Michal3,
I will guide you through activating your deleted account so that you can remove the transaction that uses it. Then, you can delete it again afterwards.
- Go to the Gear icon and choose Chart of Accounts.
- Click the small Gear icon above the table.
- Put a check in the Include inactive checkbox.
- Find the account in concern and click Make active.
You can now delete the transaction and inactivate the account after.
Let me know if you have other questions in mind. I'll be here to continue helping you.