Mail folders changed following upgrade to macos 10.15.3. Desired legacy mail folders all visible on ios 13.3.1. How to synch the mail folders between macos and ios?

afvet76 wrote:

How do I get Mail on macOS to synch with desired legacy mailbox structure for Mail on iOS?

Sync content between your Mac and iPhone or iPad - Apple ...

Uncheck and recheck Mail in the >System Preferences>APPLE ID>iCloud>Mail

If you are still having issues sign out of iCloud on both macOS and iOS then sign back in again.

afvet76 wrote:

Thank You! Success!

Thank you afvet76, glad you found the post helpful.