In Studyo, multiple teachers can be assigned to each occurrence of a section. That's the only way you can have multiple teachers on a single section, as the section's details only contains the default teacher.

Though you could edit schedules and add a teacher to each occurrence, there's a quicker way to add or remove teachers to or from each schedule. From the SECTIONS section, click the three vertical dost on a section's line and select "Edit teachers".

You get a dialog with two lists: Selected teachers on the left, and available teachers on the right. You can add teachers by clicking the "+" button on their line on the right side, and remove teachers by clicking the delete button on their line on the left side.

The left list will display a green checkmark for the default teacher, and a grey checkmark for others. You can click that grey checkmark to change the default teacher. If there are no default teachers, adding a teacher will automatically mark them as the default teacher.

If a teacher is not assigned to all occurrences of the class, a notification icon will appear next to the checkmark.