Hi Tuur,
thank you very much for your reply!
Yesterday I tried to change
hlookat and
vlookat in the
scene_1 but it only worked when I remove the
MERGE KEEPVIEW that I really need.
I saw your editing at the
onstart="lookat(160,20)" and it worked half. The starting position was correct, but when I flip back from e.g. scene_2 to scene_1, I lost the spot I was observing and will be back at coordinates 160,20.
I had to copy the hlookat and vlookat BEFORE the scene_1, now it works like a charm 
<view hlookat="160" vlookat="20" />
<scene name="scene_1" title="Heating room" onstart="" thumburl="panos/1.tiles/thumb.jpg" lat="" lng="" heading="">
<view hlookat="0.0" vlookat="0.0" fovtype="MFOV" fov="120" maxpixelzoom="2.0" fovmin="70" fovmax="140" limitview="auto" />
Thank you very much!