Hey there, I miss the opportunity to show more than one note in the same layout, no matter if editor or viewer. I would suggest an additional slide view with more columns (or lines) for different notes. That would make working with more than one note at the same time much easier.
One thing you can do here, at least for editing, is to make use of the external editor functionality. I can work on several files, and see them in VS Code or in Vim, or whatever I setup as the external editor.
I just tried something really cool! I have VS Code installed, so I just went to preferences (Mac desktop version) and in Preferences > General, placed /usr/local/bin/code (VS Code) in the text editor command path field. Then, when I click on the external edit link, it pops up in VS Code (which has preview mode! So I can view as I edit without going back to Joplin. But, what’s even cooler is that if I edit 2 or 3 files, they all go to the same VS Code Window!!!. So on my monitor, where I have a certain amount of space, I can edit/visualize several notes, and have Joplin desktop in my mac window, for example.
+1 the ability to have more than one note open. It can be awkward when you want to copy text from one note to another or even create a link between notes because you have to leave the note you are editing to get the markdown link for the other note.
I found a feature request on GitHub from last year (1424) which suggested using tabs.