If you look at Global Settings under Settings - Basic, you'll see the (former) setting for "Compose Mode" now replaced by "Select post editor". Here, you can select "Updated editor", or view an overview. Or, you can leave "Old editor" (Compose mode enabled), or "Hide compose mode", selected - depending upon your current setting.
Selecting "Updated editor" gives you the former Draft Blogger equivalent of Post Editor, now available for all Blogger blogs in Production Blogger.
There are interesting changes in "Post Options".
- No "Backlinks" options.
- Real scheduled post settings ("Post date and time").
- Edit HTML ("Convert line breaks" per post) settings.
- Display HTML settings.
And two major omissions.
- Spell Checking is not included.
- Video uploads are not included.
And now, there's the option to create true static pages for the blog.
And as the new post editor becomes more commonly used, new features and old will cause new problems.
- The New Post Editor implementation of "Read More".
If you require Spell Check and / or Video Upload, restore the old post editor.
- Go to Settings - Basic - "Global Settings".
- Select "Old editor" (Don't select "Hide compose mode").
- Remember to hit "Save Settings".
And, by the way, note the term "Global Settings". If you make this change under one of your blogs, this will be the setting for all of your blogs. Also, if you just accepted membership in another blog, check your post editor setting.