Why do Notes not sync? iCloud Notes not syncing says the solution is to update to El Capitan or log out of iCloud.  But I am now on 10.13 and have had to log in to iCloud many times due to updates and new devices.  All (Macbook Pro 2012 and iPad Pro) are on the latest updates.  (Which is why the other one saying to "upgrade to El Capitan" is not helpful.)

My iPad prefs said that four IMAP accounts, one Exchange account, and the iCloud should be syncing Notes.  The Macbook Pro prefs say the same.  But Notes I create on the iPad never appear on the Macbook Pro.  (And vice versa.)

Wondering whether having them on more than one account might be a problem, I tried to turn Notes off on the IMAP accounts.  Two accounts did it silently, but the third warned me that it would DELETE Notes from the device.  Since they aren't apparently anywhere else, I declined.

How can I get Notes to show up in the Notes app on both devices?  Preferably the most efficient way in terms of storage and bandwidth.
Open Notes on your MacBook and in the top menu, select:

Notes -> Preferences

You will see a drop-down selector labelled "Default Account:".

Make sure to select the iCloud account.

Then, while still on your MacBook, look at the left bar of your "Notes" app. You should see your IMAP and iCloud accounts there. If you do not see a left bar, then click the "sidebar" icon in the Notes toolbar.

Click on each of those sections and drag the notes into the iCloud -> Notes section.

Now, all of your notes should be on your iCloud account.

Then, on your iPad, go to Settings -> Notes -> Default Account, and set "iCloud" as your default account.

If this fails, please post a comment with details, and I will try to assist further.