+1 for draw.io (now named diagrams.net)... The best part of this app is that it has a simple embed mode, where you only invoke the editor itself (all the data related to the diagram could be stored in ClickUp itself and nowhere else). Draw.io itself is open source, so you could have your own installation and not even rely on draw.io's embed.... And honestly, it is one of the most versatile diagramming apps I've seen.

Would love to see a Docs native draw.io diagram content creation capability so that versioned diagram content could be stored within Docs alongside associated content and not having to bother with storing source diagram content securely elsewhere and attaching or embedding read-only exports of the content within pages in Docs.

Yes! This can be definitely useful!