Spell check an entire diagram
As diagrams.net is a browser-based application, there is no way to spell check all of the text in a diagram.
Instead, you should use the built-in browser spell check features. The text must be editable for this feature to work, such as when you edit a label.
We recommend that you enable the feature that checks spelling and grammar as you type, so that every time you add or change a label, it is spell checked.