Why are my existing Reminders and Notes not saved to iCloud on my Mac?
Solution 1:
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.