Hi there, SMI.
Thanks for reaching out for support here in the Community. I'd be glad to answer your questions about creating invoices from estimates in QuickBooks Desktop.
For the first question, the inactive status is in place to serve as a reminder that particular estimate is no longer needed. Estimates are non-posting and won't affect your accounts, even after invoices are created from them.
Secondly, there isn't a way to automatically transfer the estimate number to the memo box of a newly created invoice. This would need to be done manually instead. As you mentioned, you can check into the transaction history to view the estimate number, however I do see how it would beneficial to be able to do this automatically. I recommend submitting feedback to the Product Development Team for review. Here's how:
1. Click the Help tab from the top menu.
2. Select Send Feedback Online.
3. Choose Product Suggestion.
You can check out the Firm of the Future site for upcoming product updates and feature releases.
Please don't hesitate to reach back out if you have any other questions. I'm only a comment or post away.