They are on different ports because the should be.
Each of the USB to RS485 chips have a "burned in number." One of my Lynx dongles is DPB3LBJP. The others are all different and unique. My EntecPro is EN093198. Also different.
When you plug it into a Windows PC, it gets scanned, logged and assigned an available COM port. AVAILABLE is the key.
I have two computers, one to run the show, the other to program and possible back up. When I first plugged in a Lynx dongle, it was assigned a different COM port on both. I immediately edited the settings so that each specific dongle ALWAYS gets the same COM port on both machines. I use LOR S3 and it makes things much easier that way.
But, to your original question - Windows really won't let you assign them all to the same COM port. It will fight you and you will lose. Instead, just mark the 8 digit code and COM # on the side in Sharpie and carry on.