Hi Mark, so for v3 setting up the side pane like that would have involved editing the SidePane.htm file as described in these links:
http://moi3d.com/forum/index.php?webtag=MOI&msg=8064.1

For v4 it's possible to set up a startup script that will do that, I've attached one here named SeparateSidePanePalettes.js . If you place that in your MoI v4's startup scripts folder I think that should do what you want without needing to edit any files.

The startup scripts folder is in your MoI appdata folder, on Windows that would be C:\Users\<username>\AppData\Roaming\moi\startup and on Mac ~/Library/Application Support/Moi/startup.

- Michael

EDIT: updated script to work with the Oct-27-2020 v4 beta.