When I open Log Files, and open a .log, that window sticks to the foreground..wich sometimes can be mighty annoying. Is there any can to have it open in the background too, so I don't have to minimize everytime?
But why would you want to open it in the background, if the very point of Tools,Log Files...,View is to, well, view them?

( Note that you can only view one at a time anyway. )
Probably the easiest solution is to instead click the Edit button if you wanted to view multiple log files.
But just to answer your question.. you can have the window automatically minimize so that you can see the Log Files window again, then you can restore it once that Log Files window is closed.
Sample code (which has some fun behavior if you manually go to the log view window afterward):
on *:active:*:{
if ($active == @View) {
if (%lactive) { unset %lactive }
else {
set %lactive $lactive
window -n $active
}
}
elseif ($active == %lactive) { window -r @View }
}