I did also notice when I made a alternate button on my selector window with the mercenary info window for my buff list, the window can be opened and placed anywhere and stays in same spot, but has a different type of command to open the window from the merc window itself.
<EQType>mercenary/ManageWnd/InfoButton</EQType>
<Button item="SELW_InfoButton">
<ScreenID>InfoButton</ScreenID>
<EQType>mercenary/ManageWnd/InfoButton</EQType>
<RelativePosition>true</RelativePosition>
<Location>
<X>208</X>
<Y>0</Y>
</Location>
<Size>
<CX>26</CX>
<CY>26</CY>
</Size>
<Text></Text>
<Style_Transparent>false</Style_Transparent>
<Style_Checkbox>false</Style_Checkbox>
<TooltipReference>Show Current buff List</TooltipReference>
<TextColor>
<R>255</R>
<G>192</G>
<B>80</B>
</TextColor>
<ButtonDrawTemplate>
<Normal>A_BuffBtnNormal</Normal>
<Pressed>A_BuffBtnPressed</Pressed>
<Flyby>A_BuffBtnFlyby</Flyby>
<Disabled>A_BuffBtnNormal</Disabled>
<PressedFlyby>A_BuffBtnPressedFlyby</PressedFlyby>
</ButtonDrawTemplate>
</Button>