Can't lengthen slur when grace notes are present.
S3 - Major
When adding a slur to a group of grace notes, it is impossible to extend them beyond the first two. Oddly enough, this extends to adding a slur to a note before the grace notes. In this second case, once the slur hits the first grace note, it refuses to be extended beyond it using the standard Shift + Left/Right keystrokes.
#279131: Cannot add proper slur to grace notes when there are more than one.