The iOS version 3.06 release notes list the ability to save custom data from a PC to the cloud and loading it from the cloud to an iPad. I haven´t been able to find where this function can be activated. Can anyone help out?

You didn't mention in which product you couldn't find the option. In SkyDemon Plan it's under the Setup menu, in the section about Custom Data. In iOS/Android it's under the Setup menu, in the Cloud dropdown.