I have not tested a lot of the functionality of the pre-release yet but I have a noted a few things about the new layout.
(1) A "Code View" button has appeared which toggles between "traditional" and "WYSIWYG" modes. In the screenshot Jopin is in "traditional" mode and so there is also a "Layout" button which works as it did before. The WYSIWYG editor is in its really, really early stages of development. If this button is to make its way into the main release would it be possible to have the ability to switch this off in settings and also have it switched off by default? This button is inviting users to use what is still just an experimental feature. I just feel it should not advertise itself on the main toolbar until it no longer experimental.
(2) These features (External Edit, Tag Note , Note Info) have been moved to the left of the note title (4) and so can push the title some distance away from the left edge of the note (3). It's a personal opinion but this does not look right. The note title is important information. Previously the user was shown the notebook name (when selecting by tag) followed by the note title. That made sense, this doesn't. It's possibly a bit more logical to move this to the right of the note title so the information is presented Notebook - Note Title - Note Actions (External Edit, Tag Note , Note Info)? Alternatively put the Notebook name before the tags so this bar will show all the locations of the note? Admittedly the release notes do say:
It might be tweaked or moved later on once we have a clearer idea of what we want to do.
+1 to tweaking or moving...
(4) Speaking of the title, to me the reduced font size looks better than before.
(5) The above screenshot is from a note displayed with the layout as viewer pane only, yet it has an editor bar? IIRC that's going back in time. Also if you do press a button, say Bold Joplin adds the text **StrongText** at an apparently random point in the note which IIRC was an old bug...
(6) Back and forward arrows. There is no (6) in the screenshot because there are no back and forward arrows either Without the ability to have multiple note editing the navigation arrows were useful, a bit erratic, but useful.