Unfortunately LoadingMode=2 did not make any noticable difference. Thanks anyway for trying to help.
Tried adjusting the Zone entry in [G42 I1] as follows:
[G42 I1]
Name=Page PositionKeeper
Type=1027;Menu page
ItemID=0x42000000
ParentID=0x0
Pos=0,0,1024,768
Zone= 0 768 1024 768 2 1 0x0 0.5 -0.5 0x42000000 -0.5 0.5
220 0
LoadingMode=1
As a result the Position Keeper appeared visible (like pulled out) right from the start when going to TBT or Periscope view, exactly like I wanted it. BUT as a side effect, when clicking on the Position Keeper drag-out-tab, the PK vanished completely "outside" the screen beyond reach for mouse dragging it back. The drag-out-tab was off-screen, too, so there was no way to bring it back.
Any ideas?