Adding accidental to trill line causes display to jump to start of score
Select a note so that you cannot see the start of the score and add a note with a trill line (from the lines palette) - all is well to this point
Select the trill line and add an accidental to it from the palette
Result the display jumps to the start of the score
The only way I've found to return to seeing the trill line is to remember the measure number and use ctrl+f to find the measure. See #309971: Accidentals added to trill lines not displayed until redraw for other issues with the accidental.