Setting multi-row tabs in preferences doesn't work in v15.0.1.
If yes, please tell me the trick.

Regards
BS

Note that there are 2 settings for multi row tabs:

Preferences > User Interface > Appearance > Settings for Single Document Interface > Use multi row tabs (for SDI tabs)
Preferences > User Interface > Options > Use multi row tabs (for all other tabs)

The Appearance setting was missing.
Thanks