There's an option in preferences to assign user-defined command to double-click on file display background. It would be great to have an option to define command for double-middle-click.
For me it might be "close tab" as an example. And I already use doubleclick very often for "go upback".
You could probably use @keydown to make the left-double-click action do different things if Ctrl / Alt / Shift are held down, if that's any use.
If my hand was on the keyboard, I could use Ctrl+W to close tab. 
I will post this as a feature request.
Did you remove feature request form from the website?
Everything's done through the forum now, and linked accounts.
I used Autohotkey to make use of additional "key" (scroll right) on my mouse to close hovered tab (I mean you only need to hover lister background, not tab on the tab bar). Note that you need to configure Ctrl+W to close tab for this script to work.
Anyway, It would be very nice to have option to use double-middle-click.
WheelRight::
MouseGetPos, x, y, hoveredWindow, hoveredControl
If (hoveredControl=="dopus.iconfiledisplay1" || hoveredControl=="dopus.iconfiledisplay2")
{
Send {Click}^w
}
return