In order to filter a Timeline, you first need to be on the Timeline screen. You can navigate there by either going to the main menu and selecting Insights and opening up the Timeline or by selecting Timeline on the Action Bar on the Points screen.

Timeline settings allows you to enable Separate Rows. When a Point is recorded for multiple students (or multiple Points for one or more students), you usually see a student's name and "4 MORE" listed next to the student (example below). Turning Separate Rows to "on" places all of those students onto their own row in Timeline, and separates the rows if you need to download a Timeline CSV as well.