Dear Sull A,
Greetings! Thank you for posting in Microsoft Community. We are happy to help you.
As per your description, it will not let you enable AutoSave on an Excel Document with embedded objects.
We did a quick test in Excel from our side and found we can reproduce the same situation when the Excel file has embedded object.
Per our searching and test, we're afraid there is no workarounds for this scenario. We do understand the inconvenience caused and feel very sorry about it.
Personally I completely agree with you, it would be definitely ideal if we can enable AutoSave on an Excel file with embedded objects. Thank you for bringing thing to our attention.
We sincerely recommend you vote for this similar idea in Excel Feedback Community: Auto Save w/ Embedded objects · Community (microsoft.com) Our Product Team is in-charge of the site and they are constantly checking the comments and feedback from our customer. Many features have been developed and improved based on users' comment.
Thank you for your cooperation and understanding!
I hope you keep safe and healthy always.
Sincerely,
Tina | Microsoft Community Moderator