I teach introductory statistics and one of the most common symbols that we use is an x with a bar over it, the symbol for a sample mean.
Currently, this symbol can only be created in the advanced equation editor:
This requires knowledge of LaTeX. The vast majority of my students are not statistics majors so they have no experience with LaTeX and it's really extraneous to the course so I don't want to spend too much time teaching it to them.
It would be awesome if the \overline function was added to the basic equation editor which is easier for students to use.