A friendly redditor helped me out with the question.
The answer that worked is as follows:
ChicoSuaveIII 12 minutes ago - https://www.reddit.com/r/photoshop/comments/dr71c5/how_do_i_make_an_offset_line_and_then_fill_the/?
Why don't you try this:
1 First, rasterize the image.
2 Use the "Wand Tool" to select the blank area around the two figures.
3 Next, use the "Expand" and "Contract" options under the Select/Modify menu to adjust the distance you want from the figures.
4 Once you have the right distance you want, under the Select/Modify menu again, choose the "Border" option and choose a thin border, maybe three or four pixels.
5 Use the Fill Tool to fill in the border with whatever color you like.
I just tried out the above myself. It does work.