Currently, the middle mouse button does not seem to be configurable and does a lot of things. Opens folders/links in the background tab, opens archives in a tab (quite slow btw), opens files with a second application in the priority list. Maybe there is more, there seems to be no place to learn about its function.
There are people who want to select files with mmb, paste files or whatever. Can we get the ability to configure the function of the mouse buttons, especially the middle one? I just love the ability to open files in another application with the middle mouse button, but it is now impossible to do this with archives and folders.