Hi Matthias and Julia,
yes, I have a solution that works better. Meisterplan supports the user in exactly this question, i.e. how to replace a resource for a limited period of time.
This feature is a little bit hidden, but be sure that as a UX designer this is a thorn in my side and I will fix it!
To the solution:
First you right-click the resource and select "Replace Resource". In the next screen (see below), you can see that a part of the gantt is darkened. There are two black