writer: open multiple docs as tabs instead of separate windows

I know LO 6.2 supports this, but can’t get it working. I want to open multiple docs as tabs in a single window. Instead of opening new windows for every doc.

LibO never supported that. See for example:

Bug 37134 - Tabbed UI: Document-per-tab (similar to Firefox, Opera, gedit) MDI

Bug 31481 - [RFE] Split pane in same window for side-by-side proof reading/ translating of 2 different files