Multisport Aktivität mit mehreren und flexiblen Durchgängen

not sure I understand. There only two differences between the two options: A multi-sport activity allows you to set transitions, which the Change Sport option doesn't. The Change Sport options pro is flexibility - you can choose any activity; whereas the multi-sport is locked in to sport activities you proscribed when you created.

i.e. Multi-sport - create triathlon - swim, transition, cycle, transition, run. Of course you don't have to use transition, but lets say they decided to add in climbing wall to end. This would then not work as not part of your created multi-sport. unless you create ahead of time.

i.e. Change sport - swim, change sport, cycle, change sport, run. The pro of this is if they decided to add climbing wall, you just change sport and select Climbing wall.

For an official event that you know is specified then create a multi-sport activity is the way to go; however for casual stuff and training then change sport may be easier to use due to its flexability.

Marcel said:

BUT: via Change sport, only individual activities are offered for selection and no multisport activities; would have been too nice.

When you change from one individual sport to another, the two sports (or any other number of disciplines) will be recorded as a single Multisport activity automatically. You do not need to have a dedicated Multisport definition activity for it. 

You are right! It is not necessary to have a Multisport activity within the "change sport" selection. Anyways it could be there (why not). 

In a multisport activity, you are additionally bound to the order of the activities. That is the point.
For example, multisport with cycling - mountain climbing - stair climbing.
But now I want:
Cycling -> x times: mountain climbing - star climbing -> Cycling
With the multisport activity defined above, however, I also have to run through the cycling activity with every repetition (so i always need to end it immediately).
If I were to define the number of repetitions of climbing - stair climbing, then I could define a corresponding multisport activity. This problem can be solved by changing the sport acitvity!
I have now realised for myself that my personal statistics make more sense if I separate cycling and "walking" activities. For example, because of the average overall speed. Training focus for me is mountaineering and not cycling.

My solution:
Start and finish cycling
Multisport (mountain climbing - stair climbing) with repetitions
Start and finish cycling

Optimal solution; unfortunately not possible:
Start cycling and pause
Multisport (mountain climbing - stair climbing) with repetitions, start and finish
Continue cycling and finish.

as stated - for what you want to do I would suggest setting a hot key to "change sport" then use that.; as you can then do what you want i..e start cycling, then use "change sport" hot key; select climbing and when done press hot key combo for Change Sport and select cycling when done select stop.

The only issue is I am not sure how you are doing repetitions? if built into a workout or using intervals or something like that, it isn't feasible within a mullti-sport whether a set multi-sport or whether using a Change sport option. Change sport does at least allow you to use it on the initial sport (for the first time only, as at that point it isn't recognized as a mult-sport until you press the change sport hot key and start another sport activity).