Originally

Let's remove the full 2-pane layout for now and just allow PDFs to open into a separate read-only pane. We can revisit more complex layouts later when we're ready for more testing. Alternatively, we could consider adding a PDF reader as a 3rd element on the left sidebar, though that might be more complicated for now...

We already have the implementation support for "flexible left/right tab panes", allowing any file to be opened in any tab (including open the same file in both panes) and also split (i.e. move file to the other pane).

So this issue will only restrict the usage in order to simplify the interaction with files in the editor.