Latex Plug-In for Final Cut Pro

I'm not aware of any but have not had the need to deeply research. Depending on what you're trying to do, maybe animating LaTeX equations in Keynote and exporting to FCP might work?

About LaTeX and MathML support in Pages, Numbers, and Keynote - Apple Support

Add mathematical equations in Keynote on Mac - Apple Support

I doubt it. However, you can use Pages.

Go to the Insert dropdown and select Equation:

Example:

x= \frac{-b

\pm \sqrt{b^2 - 4ac}}{2a}

Click Insert.

Use Command-Shift-4 to do a selection screen capture and you can import the image into FCP. Result:

Be sure to set your font and font size before capture in Pages.

That's about as close as I've been able to find... On the upside: Pages is free.

The square root from your equation shows in Pages and Keynote version 14.1 on MacOS 14.5.

If you aren't using it already, try LaTeXiT.

Rather than having to do a full LaTeX document, you can type just the code for the formula you want, and copy it or save as png, potentially with better quality than a screenshot, and including transparency - which a screenshot won't provide. You can adjust size and color of your formula directly in LaTeXiT.

Don't let the lack of the square root symbol throw you - I'm "stuck" in OS 10.14.6 (Mojave) and Pages 10.1... This could just be an issue with this particular version of Pages. (Same info about my version of Keynote...)

I figured as much... There was some *funky* "security" update for mojave (pegasus??) awhile back -- it screwed up several things INCLUDING color pickers in Final Cut Pro and Motion. Since then I've had to use the System Color Picker in order to change colors... :P When I run into a problem like this... that's what I blame.