It wont be an exact outline but instead a bounding box (or whatever type of adornment you choose.) From my understanding this is the closest to a highlight you can get in Roblox at the moment.
What about around MeshParts? They all have different shapes and every selection/handle instance tends to be locked to one shape like a cube or a sphere
You can do it thanks to viewport.
How it would basically work is that you make ViewportFrame inside ScreenGui, and you scale viewport to whole screen. then you will clone every single part you want to be highlighted inside this viewport, and then you just need to set CurrentCamera of your viewport to the workspace.CurrentCamera.
I recommend watching this video as it is based on that:
I mean, yes, but it is a workaround + since it would copy parts locally, it might lag only for people with bad performance device, but you could make it turn on and off. Also it would depend how many parts you want to highlight.
It all depends on how you want to use it.
I believe highlights works similar way anyway, so this is just a way to not reach any limitations highlight is used on the left, viewport frame on the right, result is similar
When exported it into studio I just colored the inside out face neon and white…
This method doesn’t use Scripts, and could be useful for smaller case scenarios. But if you have something that has a high mesh Triangle Count. Then I don’t recommend just duplicating itself on another due to performance issues. This also applies to any image texture you have with the model.
Granted this also has a different look from the highlight, so it really is just whatever you think would fit best with your situation.