And now that I've gone back from the account upgrade to the file the undo button is completely greyed out!

OK. Managed to fix this by upgrading to team. Using the revision history to go back a version. Restoring that then. Downgrading again. Not sure what it cost me but hopefully not too much. Just wish the undo button worked or revsion history wasn't a team only feature.

Hey Neil thanks for posting in the community! We're glad that you were able to restore to a previous version of your document but we want to ensure you're having a great experience using Lucidchart. Apologies for the difficulty using the undo button! While we're currently not able to reproduce any issues with it I suspect that you  might not have been able to undo because the layer deletion occurred in a different editing session that when you discovered it. We would be happy to look into this further and definitely want to know if you experience any additional trouble.

Thanks for the response. It was definitely the same session. When you clicked Undo it simply said saving then nothing changed repeated clicks did the same. You need the ability to do multiple undos at the same time from a menu like Excel does. But really you need to make revision history a feature of the individual package. It's unclear to me why this would only be for teams? As those editing their own docs independently like me would really use the feature. 

Thank you for clarifying and I'm sorry that the undo feature didn't work as it should have for you. If you experience something like this again please reach out to our product support team here so that we can dive in on the specific document and take a closer look.

Thank you for the thoughtful feedback about revision history. If you'd like to share your thoughts on this with our product development team please add them to this form.