I am aware that in general installing addons in TOR is not recommended but OurStickys addon seems like a basic (and very useful) addon: https://addons.mozilla.org/en-US/firefox/addon/ourstickys/
The privacy details in "About this extension" is very clear: "Privacy is very important to us. We do not store any sensitive information and we make sure that the information is not accessible by anyone. No third party web application, nowhere to register, nobody to trust your data with. NO DATA in any form will be shared with anyone."
So, is it safe to install OurStickys addon?