PM_ROLLUP_BUTTON
From EDM2
Adds a new button to the window titlebars that you can use to "Roll up your PM windows to just a titlebar". This setting worked in the MERLIN Beta, but seems to be disabled in WARP 4 GA.
Note: WARP 4 only.
SET PM_ROLLUP_BUTTON=<value>
Example:
SET PM_ROLLUP_BUTTON=YES
Parameters
Value; YES or NO.
Source: Team OS/2 WEB pages