Rated 5 out of 5 stars
XNote as installed in TB 3.0.x WILL NOT survive an upgrade to TB 3.1. THE INSTALLER GIVES FAIR WARNING OF THIS and if you choose to continue, XNote WILL BE DISABLED!
I inquired with Lorenz Froihofer and he had this to report:
"Currently, I don't have the time to investigate this. Probably the extension works as is and just needs to be allowed to be used with TB 3.1. You could try that for a TB 3.1 test installation. The only thing you have to do in order to make XNote install on TB 3.1 is to extract the installation file with a ZIP-extractor, change the line "3.0.*" to "3.1.*" in install.rdf, ZIP it again, rename .zip to .xpi, install it, and see if everything works. If no, we need to upgrade the code."
I uninstalled the XNote running in my current TB 3.0.4 and then installed the extension modified as above. The update to TB 3.1 went smoothly without alerts and XNote works just fine!
Even though it worked for me, proceed at your own risk.