How the fuck do I use XCloud?: A Troubleshooting Guide
So, the old XKit is slowly becoming obsolete, but you don’t want to lose your settings when upgrading to the new XKit. Well, congratulations! You don’t have to! Contrary to rumors flying around, XCloud still works. You can upload your settings to the XKit server and get them back once you’ve downloaded the new version.
Let’s get to work, shall we?
Backing Up Settings
1. Open the XKit Options Menu and download the XCloud extension.

2. Register for your XCloud account.

3. Sign in to your XCloud account. Afterwards, you should see this screen:

4. Click Sync. Click the shield and press “Load unsafe scripts”. The window will refresh.

5. Navigate back to the XCloud Sync page and attempt to sync again.

You have successfully gotten your settings onto the XCloud server!
Now you’ve got to get it back. Once you’ve downloaded the New XKit and installed XCloud from the extensions gallery, you’re ready to restore.
Restoring Settings
1. Click restore at the main menu to begin.

2. If you get an error like this:

Then you have an outdated or custom extension. If you have No Sidebar or Estufar’s Sidebar Fix, you will need to uninstall them in order to proceed.
3. After that, you’re good! Congratulations, you have your settings safe and sound!

Lots of thanks to this person for writing a guide. You can upgrade to the new XKit safely if you follow these steps :)