Pane Split Remembered Wrong

Reproducing Steps:
1. Turn on the option "Put editor on the right".
2. Move the pane splitter to the right.
3. Close window.
4. Re-open a window.

You will notice is pane splitter is on the left now.

Reproduce the issue in MacDown on macOS using the listed pane-splitter steps, then trace where the splitter position is saved and restored when the window closes and reopens. Done means the splitter remains on the right after reopening when the “Put editor on the right” option is enabled.

Written by the indexing model from the issue text.