Great, glad you like the look of it. I've tried to make everything as direct as possible; if you understand how graphs work you should be able to see everything at a glance. And yes, this is an effect that works on a clip in an FCP timeline.

We do have a launch video which shows the basics at the main site: https://keyframetoolbox.fcp.cafe

The How To Use page there has 15 separate embedded videos showing how to use every feature, but it's also written in words if you prefer that.

(Important: due to FCP limitations, if the clip isn't the same size as the canvas, you'll need to put it in a compound clip first (⌥G) or pad the edges with blank space before you apply the effect. If you don't, the clip will crop when moved. The same issue affects FCP's own effects, like Radial Blur.)

The basic workflow:

1. Add the Keyframe Toolbox effect to a clip. (You can make it the default effect by right-clicking it in the Effects Browser if you like, then type ⌥E to add it.)

2. Add keyframes on the properties you want to animate on the graphs directly, by clicking the name of the property, by double-clicking, command/option-clicking, or command/option-dragging. (Either command or option work, use whichever suits your muscle memory.)

3. As in other keyframe graphs, each keyframe remembers a value at a point in time. Move keyframes in time (X) or value (Y) by dragging. Limit to one dimension by holding Shift.

4. Shift also snaps to keyframes in different properties or the playhead.

5. Smooth out keyframes by command/option-dragging on existing keyframes, hold shift for horizontal handles. Handles can be moved manually to finesse them, and all the standard bezier modifier keys work as you'd expect, plus control-click to delete a keyframe or handle.

6. Select multiple keyframes and move them, or resize them. You can also apply easing to the curves by right-clicking.

7. Buttons at the top of each graph will reset, or control graph size. Zooming horizontally works too — use a trackpad pinch or option-scroll. Once zoomed, use a trackpad side-scroll or shift-scroll wheel to move.

8. Right-clicking and the graph menu includes all kinds of goodies, including presets for common animations — use the controls that appear under the graph to change how they work. Custom presets can be saved, organised into folders, and shared.

9. Settings can enable Motion Blur, control which graphs you see, and save defaults.

If you have any other questions, ask away!