I will post my project in the next day or so, but I believe I solved the problem.
I would like to become more adept with javascript but being as I’m not coming from a coding background my first inclination is to find a non-coding solution, which is really what Hype is made for. It’s not that the coding solution is more time-consuming, but I preferred creating multiple timelines to achieve the effect.
I needed two things to happen. One, a click on a thumbnail would slide the row of images as much horizontal distance as required to get to the image selected. Two, a click on an arrow would advance the row of images by just one image at a time. I just didn’t immediately understand how to connect them.
Relative timelines worked for the thumbnail timelines. I made each thumbnail its own relative timeline, and animated the “row of images” group, starting with the last image (in the row) in view and animating to reveal (through the “mask” group) the image corresponding to the thumbnail selected, ending on that image. The action is on click ->start timeline.
I also created the main timeline, animating the image row from the first image to the last, with timeline actions pausing the timeline every half second. The action on right arrow is on click->continue timeline->Main Timeline; and left arrow on click ->continue timeline->play in reverse->Main Timeline.
My breakthrough solution was to put timeline actions at the end of each of the thumbnail timelines.
The timeline action is: Go to Time in Timeline->Main Timeline->(The timecode corresponding to the pause time when that particular image is in view). First image is: 00:00.00, second image is 00:00.15, third image is 00:01.00, and so on. So, when we jump to that main timeline, a click on an arrow advances the row of images group in one direction or the other, one image at a time. Going back to clicking on a thumbnail plays that thumbnail’s relative timeline, advancing the row to show that image, and then (unbeknownst to the user) jumping back to the same image in the Main timeline, allowing the one by one image advancement.