You can find the pixel mapper tool thread and links here:
To use this, you’ll want to arrange your LED strip in a heart shape, light it up so the pixels are easily seen, and take a photo. Then use the tool to click on each in order starting with the first pixel. Copy the entire text area contents to the Pixelblaze mapper tab, and you’re set!
There’s probably a way to generate a heart outline coordinates with some code that would be more precise, but you’d have to make it match what you create in the real world which might be trickier than the build + photo + click approach.