We're aiming to release a new version this month, and one of the last things to be added is obtaining and utilizing animal tendons in the making of sinew yarn.
This is nicely linked to ongoing improvements with making of clothes as it's been traditional to sew leather and fur clothes with sinew yarn.
In the game other type of yarn will just as well, but being able to produce sinew yarn will surely come in handy in many ways.
Compared to spinning plant fibres into yarn making sinew yarn is quite a lot slower process as it needs to be done merely by hand. However, availability and rather easy processing of animal tendons into sinew fibres is in favour of producing sinew yarn.
One downside of sinew yarn is that you can't use it for fishing gear as it comes loose when getting wet. It's yet to be decided to what extent and how we'll be manifesting this in the game world. Groundwork of obtaining tendons, drying them and separating the sinew fibres is now laid out, and soon enough I think we'll be seeing some preview screenshots too.
These are future features - not yet functional in current version 3.86.1