You may create angular line (not create bezier handles in points) and than use function smooth line.

M.

13. 7. 2022 v 22:10, Tarquin Wilton-Jones via Therion <therion@speleo.sk>:

I was wondering if it would it be possible (and easy) to add a new line
type that is more similar to Illustrator's pencil tool?

Sorry, I do not know about whether you can draw lines like that in
XTherion.