Thanks for posting in the community! There is a 60 object limit per document for users on free accounts. If you are receiving a pop-up referring to unlimited shapes that prevents you from continuing to edit then you have reached this object limit. You will not be allowed to continue editing unless you delete some objects.
If you’re not certain whether you’ve reached this limit you can use our performance metrics hotkey shortcut (Ctrl+Alt+Shift+K for PC or Command+Option+Shift+K for Mac) to determine the number of objects in your document.
To see what else is available to you on your free Lucidchart account please take a look at our Lucidchart Plans article. If you're interested in premium features or would like to try them out please visit our pricing page.
Thank you!