I hear your sentiments, @Teacher_Man.

I can certainly see how much of a difference it would make for companies like yours if we can customize and personalize our sales forms the way we want them to be.

Like you, I am eagerly anticipating the availability of this feature. You are being heard, and our product engineers are fully aware of this. I just want to let you know that a new feature will go through extensive measures to ensure that it is fully functional before being implemented that's why we're unable to provide as to when this will be available. No worries, once a new update will be released you'll be notified through email. 

If you haven't submitted your own feedback, I'd recommend sending one so you'll be added to the list of users to want to have the availability of this feature. You can follow the steps provided by my colleague above or refer to this article so you'll also have access to our new product feature releases: Customer Feedback for QuickBooks Online.

With regard to adding signatures to your invoices, you may utilize the Attachment field on the Invoice page to insert a signature image to your invoices. 

Another option is to use a third-party application that supports this feature. You may check out one through the Appstore.

Additionally, I've included an article that you may find helpful in case you'll want to split an estimate into as many invoices as you need: Set up and send progress invoices in QuickBooks Online.

Fill me in if you have more queries about managing your sales forms in QBO. I'd be glad to assist you further. Take care.