This is the expected behavior and is being done to encourage users to try new editor as the old editor will be deprecated.
If you create a campaign, and toggle off the New Email Editor to use the Old Editor, please keep the following in mind:
- The old email editor is scheduled to be read-only starting May 31 and will be depreciated as of June 30.
- When you create a campaign using the Old editor, you can still schedule the campaign, and the Old email will save. However, if you edit the campaign again, the New Email Editor will be toggled on. In which case, simply toggle this off, and re-schedule or save your campaign.