It’s kind of tricky and sometimes I can drag if I get the mouse pointer close to this divider, but was able to repro on Windows 11.
SYSTEM INFO:
Obsidian version: v1.11.6
Installer version: v1.10.6
Operating system: Windows 11 Pro 10.0.26200
Login status: logged in
Language: en
Catalyst license: supporter
Insider build toggle: on
Live preview: on
Base theme: adapt to system
Community theme: none
Snippets enabled: 0
Restricted mode: off
Plugins installed: 0
Plugins enabled: 0
RECOMMENDATIONS:
none