Fusion not adding elements to correct clip

I am trying to add colored rectangles to highlight portions of a software to different clips. On clip 1, I click the clip in the timeline. It has a red outline. I click Fusion. I add Rectangle, Background, Merge, size and color my rectangle. Back in the Edit page, the effect is there as I would expect.
I click on Clip 2. it has a red outline. I click Fusion. I see Median 1 and MediaOut1 as I'd expect. I click add rectangle. nothing happens. If I go back to clip 1, I see it's added the rectangle to that clip instead. I cannot get it to add anything to Clip 2, not matter how I try and select the clip in the timeline.
Here's a video to show:
https://drive.google.com/file/d/1-tB24V ... sp=sharing
I click on Clip 2. it has a red outline. I click Fusion. I see Median 1 and MediaOut1 as I'd expect. I click add rectangle. nothing happens. If I go back to clip 1, I see it's added the rectangle to that clip instead. I cannot get it to add anything to Clip 2, not matter how I try and select the clip in the timeline.
Here's a video to show:
https://drive.google.com/file/d/1-tB24V ... sp=sharing