I have enabled iCloud support for Apple applications such as Reminders and Notes. Yet my existing Reminders and Notes on my device are not being saved to iCloud. Isn't the point of iCloud for Mac to offer cloud storage for application data on your Mac device? As shown below, the application data on my device do not sync to iCloud, and there seems to be no way to do it manually.
If you've created these Reminders before you turned on iCloud, then they will be local to the device. Newly created Reminders should automatically be 'in' iCloud.
(In fact, I can't see how to create a Local one on my Mac or iPhone.)
You can select an individual item, and then move it to a new List. This might be easier to do wholesale on the iCloud website or on a Mac.