When adding accidental to trill line, view jumps to start of score; Accidental appears sometime later.
When adding accidentals to trill lines, by dragging and dropping from the Accidental pallet onto the trill line
(Bars 99 and 100, Clarinet and Bass Clarinet in score for example), the view jumps back to the start of the score. After returning to the appropriate part, the accidental does not appear immediately, so it's unclear as to whether it worked or not.
After adding another trill line, then the accidental appears, but it might also just spontaneously appear later, after flipping pages, or adding additional notes. However, the view jump is also disruptive to the entry flow.
OS: macOS High Sierra (10.13), Arch.: x86_64, MuseScore version (64-bit): 18.104.22.16811, revision: 20414b2