How can I reuse an effect sequence in FCPX? I'm creating a video for my son's fifth grade class that has a large number of interview clips. In each interview, I want to show a split-screen effect with a still photo on one side and a video of the interview on the other side. I have worked out the effect I want with some transitions, a title, cropping and a couple of key frames.

But I want to reuse this sequence across interviews for over 100 kids. Is there a way to create a template or a combined sequence that I can then copy-paste and then replace the source photo and video?

I apologize if I'm not using the right terminology, but I'm new to FCPX (and video production in general).
Use "Total Adjustment" it works like a photshop-layer. You simply can duplicate it for reuse with other clips.

How to: Install Total Adjustment. Open the effect-library in Final Cut Pro X. Select the titles. Drag the "Total Adjustment"-title to your project. Copy all effects you need to this title-clip. Place it above a new videoclip. Every video-clip that's under this kind of "layer"-clip will be affected of its effects and adjustments.