What is in the next measure?

The next measure is in D major. The beginning (in C major) changes into D major after 10 bars, then continues in D until the end while skipping the bars you see in the image.

I did this by hiding the courtesy accidentals in that last measure (measure attributes) and put them back in as text expressions. That got them on the left side of the repeat bar.

In this particular case I would add the naturals as expressions.

To make room for the accidentals, use the Measure Attributes to add Extra Space At End of the measure, probably something like 12pt.

To get the naturals at the precise Vertical position, remember this:

The height of a staff is 24pt.

Hence the distance between the staff-lines is 6pt.

And one scale step is 3pt.

@Peter: I see what you mean but there are no accidentals in the Expression Tool and I can't find a way to create or insert accidentals in the 'Create (Misc.) Expression' tab of the Expression Tool.

Make sure to choose the Maestro font.

@Adrian: After widening the measure a bit, this did the trick, thanks!