- open the attached database document
- open the form therein for editing
- open the "Form Navigator" from the "Form Design" toolbar
- dock the form navigator at the right hand side of the form window
  (by dragging it to there, or by double-clicking onto some gray space of
  the navigator window)
- (maybe ensure that the docked size is appropriate - the default width
  might be 0)
- enlarge the width of the form window so that you again can see all controls
- close the form window, answer the question whether to save the changes
  with "Yes"
- re-open the form window
=> the window is smaller than before, the width of the docked navigator
   got subtracted somehow

Ugly consequences from this:
- If people really work with a docked form navigator, they need to
  constantly adjust the size of their form window
- It happens with all docked windows, for instance the stylist and the
  normal navigator. Here it is less severe, since those windows usually
  remember whether they were open or not