Docs: dragging the New button to open a session in a split pane is undocumented

Environment: Windows 11 Home (10.0.26200) · Claude Code 2.1.240 · desktop app on latest as of 2026-09-10

Left-click-and-drag the New button opens a new session in a split pane. This works, and it appears to be the only way to get a new session into a second pane. It is not documented.

https://code.claude.com/docs/en/desktop describes these as two unrelated actions:

"Click + New session in the sidebar, or press Cmd+N on macOS or Ctrl+N on Windows, to work on multiple tasks in parallel."

"To view two sessions at once, hold Cmd on macOS or Ctrl on Windows and click a session in the sidebar. The session opens in a second pane alongside the one you already have open."

Both documented split routes (Ctrl+click, and right-click → "Open in split view") only work on sessions that already exist. Plain-clicking New takes over whichever pane has focus, so the discoverable path is: let the new session take over your pane, then re-open the original beside it — which rebuilds the split backwards and leaves the sessions on the wrong sides.

The use case: I had a half-typed message in one session and wanted a new session beside it to ask a side question, without disturbing the draft and without using /btw, because the answer was worth keeping in its own transcript.

Ask: document the drag gesture, and ideally make Ctrl+click on New do the same thing, since Ctrl+click is already the split modifier elsewhere in the sidebar.