I don't know if this will help, but you might check the docs for your device to see if it has setup options.

Certain midi devices (maybe most) would seem to anticipate the possibility of multiple units, and there is a setup option to set/define the Device Number. Usually on a range of 1 to 16 (i.e. actual setting 0 to 15). My Yamaha MU90r has such an option, within 'All Part Control'. Other units may have it in a different place.

Setting this is but one thing. If you can do this, then you have to hope that when Windows interrogates the devices that it notes the Device Number as well as the Mfg ID and the Device ID.

Geoff

Has anybody a smart way to force identical MIDI devices to have unique MIDI input/output port names in Windows10?

The port names are not editable. Windows queries the MIDI interface for the description, which is what you see.
If there are more than one of the same interface, Windows is supposed to add a numeric suffix to tell them apart.
The bad news is, this is broken in version 1803 and earlier.
The good news is, this is fixed in version 1809.
The bad news is, the rollout of version 1809 was suspended when some people reported that some of their personal documents got deleted in the update. Hopefully the fix and the regression tests will not take too long.

I just want to follow up on this issue that I posted 7 month ago and describe my solution to my problem. And thanks Geoff and Eddie for good replies.

As Geoff points out the X-Touch Mini's setups can be edited with a editor program including setting a device id that is handy to distinguish between the devices. My frustration was that this device id was not reflected in the port name. After some communication with Behringer support I found out that this was not a bug and the id was mainly meant for the bigger X-Touch models that use the same editor program.

I then realized that a more flexible (yes, and complex 🙂 solution would be to have identical setups on the 4 devices except the global MIDI channel (can be set in the editor program) and process the MIDI CC streams in a dedicated cross-bay-like program where I could translate the CC messages as desired (momentary, toogle, note, etc) and map to virtual LoopMIDI ports that is used by the destination DAWs and other programs. This also allowed me to add other controllers and use the same controller in different programs.

So what to use as a cross-bay-like program? MIDI Ox couldn't be used because it couldn't save a setup with identical named devices. Then I tried the Bome MidiTranslator Pro that could do what I wanted and is relatively cheap and straight forward to use. There is a free Classic version but I'm not sure it can do the job. Finally I bought the full Max8 system on sale that can definitely do the job. It is a much more expensive, clearly overkill for this job, and have a much steeper learning curve, but allows me to do much much more. Now everything works great with a setup that can be loaded, tweaked and saved, e.g. where each X-Touch Mini is controlling both individual monitor mixes in RME TotalMix and instruments/effects/loops in Ableton Live at the same time.

So I you run into similar problems with identical named MIDI devices (and the OS do not add numbers like it should as Eddie points out) my advice is to create virtual MIDI ports with LoopMIDI ( https://www.tobias-erichsen.de/software/loopmidi.html) and map the device ports to the virtual ports with a tool like Bome MidiTranslator ( https://www.bome.com/). There may be other tools available for both tasks.

cheers /// peter