Thanks for your timely answer! I guess you understood right. But let me try to be more precise.
I want to check the effects of a shock within the VAR by restricting the x_1 variable to not move. This is because I want to see if the remaining variables continue to react in the same way. But to this end, I think (not sure) that I have to set the coefficients of x_1 in ALL the other equations equal to 0. In other words, I am trying to figure out the transmission mechanism of the underlying shock, so I have to switch off the x_1 channel. So I want not only the IRF of x_1 to be zero, but I also want that the other IRFs to not consider the reaction of x_1.
I there a way to do that using the SVAR function?