is there any way to copy a file from one playlist to another without bringing it to front ? something like "copy to background playlist" ?

thanks in advance

Yes just drag and drop it on that playlist.
I tried with playlistmanager though, don't know if it works with playlist tabs.

hm well i tried it with the playlistmanager now (didnt know that one before) but and it doesnt really help, still got two choices, either drag and drop it from one playlist to the other which normally changes the tracks position to somewhere near top of the original playlistor drag and drop it to the playlist manager window which still moves the track in the original playlist as i mark it with the mouse and pick it up
isnt there anything like doing a rightclick on the track and menu pops up "move/copy to playlist xyz" ?

i think you could do that with foosion's utilities plugin (foo_utils)!