No perfect workflow yet exists.
There aren’t great ways to add drawing blocks into Notion. There are a myriad of tedious ways, though. Any number of apps can be used to save drawings. Those drawings can be uploaded to Notion in the way of completed files. They cannot, though, be edited later.
Cmd+C → Cmd+V does not work with images.
Apple Notes
Can be opened side-by-side with Notion & Drawn into. From there, it’s “Share”, → “Save to Files”. Then in Notion, Insert image → Photo Library → Recents → select Image.
Still these cannot be updated or edited. Also I doubt the included handwriting is indexed as text.
Notation
A dude built a drawing embedding web app. It seems buggy, but technically works?