In Final Cut Pro X, there's a ton of different situations that you might want to move attributes between clips. If you're doing color corrections on footage that has an imprecise white balance, vignetting a scene, or applying a tiling effect across a dozen clips. This will save huge amounts of time with relatively little effort.
The process is extremely simple.
Just hit Copy or Command + C
And to paste, simply hit Paste Attributes in the Edit drop down or Command + Shift + V This will open a simple menu to allow you to carry over any audio or visual attributes you've added. Just choose what you'd like to move!
Just in case you're wondering why this is such a crucial move, here are two examples:
In the first, all the scaling is done manually.
In the second, everything is preconfigured and pasted in.
If you can imagine tiling 12 or 15 different videos like this, that extra ~20 seconds of work can very quickly add up!