How do I create a bold line (not text)?

Hi. I only do simple cube images without text. I would like to emphasize a bold ‘direction arrow’ for the direction of expansion but can find no way to do so. Any thoughts?

You can “model” the arrow. with black to make it bold.

Thanks. Do you mean that I need to make a “rod” with thickness and arrowhead? Would this be a problem when changing orientation in 3d?

Yes. I think it might be better as your direction of the arrow will stay true and correct to the 3D shape no matter how you orient.

Another alternative is to use Layout.

Thanks for your help. We’ll see how I go!

See @chamberz tutorial: