Hi,

Sometimes tasklist is unable to show every available main window for application (main means window that shows opened project) if I click on application group tab.  At the same time, I am able to switch to invisible window by alt-tabbing. When I do so, that window re-appears in tasklist.

I've tried to understand what forces window to disappear from task list, but with no success yet. (I do have a hunch that "invisible" window is shown in alt-tab menu as grayed out, but right now I cannot force any window in this alt-tab menu to become grayed).

Those app windows are Java app windows. 

Unfortunately, I am unable to take a screen-shot or execute an xprop for missing window since it is missing when it is completely covered by other applications.

Thanks in advance.