The tool bar at the bottom of the estimate page has disappeared and I cannot save or save and send an estimate.

Hi there, @ioct.

There are no reported cases about not being able to save and send estimates in QuickBooks Online. I can share with you some steps you can perform to isolate the issue. 

First, open your QuickBooks Online (QBO) account via a private browser to check if it's a browser issue or not. Then, try sending and saving an estimate from there.

To save you time, use either of these keyboard shortcuts:

• Google Chrome: Ctrl + Shift + N
• Mozilla Firefox: Ctrl + Shift + P
• Safari: Command + Shift + N

If it works, you need to go back to your original browser and clear its cache to start fresh. 

You may also use other supported browsers to help us narrow the cause of this behavior.

For additional guide, while working with estimates in QuickBooks Online, feel free to open this link.

If you wish to customize your estimates and other forms, you can as well open this article for your reference: Customize invoices, estimates, and sales receipts in QuickBooks Online.

Please let me know if you need further assistance with this. I've got your back and am always happy to help. Have a great weekend!