How do I track the sequence a player does something?

Hi! I'm building a game in which the player will use a sprite to collect labels (on the right side of the screen in the picture below) in a specific order.

I would like to keep track of the order the player collects these labels on the left side of the screen (in the timeline image). For example a player collects a the label "Deposition of Siltstone" and "Deposition of Siltstone" populates in the first spot of the timeline on the left. I would like for the way the timeline populates to be dependent on the order in which the player chooses to collect each label.

I am beyond stuck as to how to accomplish this. Any help would be very much appreciated! Thanks!

Let's say you have Label sprite and TimelineLabel sprite, and both objects have the same set of animations. The default animation for TimelineLabel sprite is "Blank". Then you can do this:

Player on collision with Label

.. TimelineLabel Is Animation "Blank" playing
.. TimelineLabel Pick nearest to (-1000000, 0)

...... TimelineLabel Set animation to Label.animationName
...... Label set collisions disabled

Thank you!