Hi HansWernerOlmDerDritte,
Please take a look at the solution for the similar issue
here[
^].
In the link provided above, the OP was asking about having a single report viewer for multiple reports and should select a particular report with a help of radiobutton list.
I've done the same in my previous projects and its an efficient way of handling reports instead of having multiple report viewers.
Hope this helps you out.!
Thanks you,
RelicV