Just to confirm, are you trying to delete transactions from a deleted PayPal account? If so, deleting an account from QBO that has transactions only removes the account from the list. What we can do is to reactivate your PayPal account and delete them one by one.
To reconnect PayPal:
Select Apps from the left menu, select Connect to PayPal in the search field.
Click the Get App Now button.
Select the Let's do it button.
To authorize Intuit to pull data from your PayPal account, select the Give permission button.
Enter the email address associated with your PayPal account then select Next.
Enter your PayPal credentials then select Sign-in.
To authorize the sync, select the Agree and Connect button.
Once the connection is established, you will then select Return to Intuit.
Select the account where you'll find your PayPal transactions, select Next.
Select the Sales tax rate that will be applied to all imported Sales transactions then select Next, then Done.
Once done, delete the transactions individually.
Doing these steps should let you remove them from the account.
If you're referring to something else, please add a comment down below. I'd be glad to assist you further with deleting transactions concern.