Noticed the same behavior before, so this is an old issue.
- I open a custom Passage Guide, it opens to fill the left panel
- I open a new Passage List, it opens on the left panel, adding a new tab
- I drag the Passage List tab down, trying to put the Passage List on the bottom with the Guide on top. It refuses to create a new panel on the bottom but it will create a new panel at the top.
- I drag the tab to the top, moving the Passage List above the Passage Guide
- I then drag the Passage Guide tab to the top, placing it above the Passage List
It looks like you cannot create a new panel below a guide, though you can create a panel above a Guide. Also, you can move a guide above some other panel.
