I'm using Xcode 13.2.1 which suffers as well of this issue, typing text is visibly slow. Things improved dramatically after disabling "Code folding ribbon" from Preferences > Text Editing.
Gottlieb
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The "tiling" word from that slide mentions how they internally implemented PKCanvasView. If you "Debug View Hierarchy" in Xcode, you'll see that there is a tiling view among other subviews of the PKCanvasView.Tiling is not a feature that's available to developers directly. I believe there is a chance to achieve this by hacking responder chain, so while stroking with Pencil check if it's off the current canvas bounds, if so, pass touch events to the next canvas.
In the storyboard, add a UIView object over the view controller's view. Then set this new UIView's Class property (from Identity Inspector) to PKCanvasView. That's it.