Markers can be added at the top of the timeline to help you locate important frames.
Double-tap on the ruler at the top of the timeline to open the markers panel.
Marks IN and OUT set the limit of the portion of frames that can be played and exported.
Long-touch a marker and drag it to move it to another frame in the timeline.
Double tap on an existing marker to rename it, change its color, or delete it.
You can choose to have the markers names displayed at all times: in the Settings, go to Timeline and enable the option Always show markers description.
To flip between markers, in the settings, in the Flip tab, choose Markers as the flip style.