Hi Reto,
if you need to have your subvi at the same screen position as the main vi (hiding it) you could do this:
Get a reference of the main vi, feed it to the subvi. In the subvi you can read the properties of the main vi (window size and position) and adjust the properties of the subvi accordingly (all by using property nodes). You can also hide the main vi by hiding it (property Front Panel Window:State)...
Best regards,
GerdW
using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019