Adjustment layer and text items have black rectangles on them in timeline

[Cameron22527877lpb4]

Not sure what happened but all of my non-video or audio items on my timeline have black rectangles at the beginning. See screenshot below. What does this mean? Can't find anything about this through searching or googling.

[Cameron22527877lpb4 · Accepted solution]

Nevermind, I'm dumb. I somehow accidentally turned on "Show Video Thumbnails".