How do music editors indicate changes they've made to a score?
Sometimes an editor will make musically meaningful changes to a score, such as
- Adding markings the editor believes were omitted by the composer or previous editors;
- Modifying notes the editor believes were errors or omissions from previous editions;
- Including markings where there are multiple possibilities based on earlier editions and where a definitive answer is not available;
- The editor's interpretive opinion.
Such markings can lead to confusion and, thus, to questions here on SE Music Practice and Theory. The purpose of (the answers to) this question is to provide a hub linkage point for questions that stem from editorial score emendations.