Hi there, Tezz3404.
Thank you for reaching out to the Community. Yes, editing or deleting estimates in a closed book period in QuickBooks Online is possible. The platform is designed to allow for changes to be made even after the books have been closed. However, you've mentioned that you were prompted to enter a password. If you were prompted to enter a password and you're an Admin on the company, there's no need to contact your accountant to bypass the password. Instead, change the setup in the settings and select the option to Allow changes after viewing a warning. This will prevent any further prompts for a password.
However, If you are not an Admin, you'll need to ask your accountant for the password to bypass the prompt message. It's important to have the necessary permissions in order to make changes to estimates in a closed period.
Also, I've checked your post and found that you've entered similar concerns twice. Please know that my colleague already answered the duplicate one. You can view his answer through this link: https://quickbooks.intuit.com/learn-support/en-us/other-questions/re-deleting-estimates-in-a-closed-...
I'm adding this article to see different info on how the Sales page gives you a great at-a-glance view of sales transactions like open invoices and paid invoices: View sales transactions.
Please know the Community has your back. If you have more questions about the estimates, post a comment below. I'll be right here to answer them for you. Have a great rest of the day.