I have another suggestion of placing a leading sticky widget on each track & the timeline like this. The widgets can either be scrolled away with the tracks, or it can be sticky too.

The width of the leading widgets must be provided (assert) to the TimelineEditor like this, if the user provides at least one leading widget.
TimelineEditor(
leadingWidgetWidth: 100,
stickyLeadingWidgets: true,
timelineLeadingWidget: Text('I lead timeline'),
trackBuilder: (track, pps, duration) => TimelineEditorTrack(
leadingWidget: Text('I lead this track'),
),
);
I have another suggestion of placing a leading sticky widget on each track & the timeline like this. The widgets can either be scrolled away with the tracks, or it can be sticky too.
The width of the leading widgets must be provided (assert) to the
TimelineEditorlike this, if the user provides at least one leading widget.