If I have an oddly shaped piece of material, I will often take a photo of it, and trace it to scale in inkscape, to do my layout there. Any time it takes to do that is completely made up by inkscape’s better arrangement tools, especially when dealing with a design that is many small parts.
If I am working with a piece of non PG hardwood, I’ll just make a rectangle in inkscape that matches the size of the material and do my layout inside that. At the end I’ll either delete the outline, color code it so it can be ignored, or even remove a couple sides to make a corner jig if my fit is particularly precise. None if this is nearly as easy to do in the GF UI.
Then on importing to the UI if I spot an issue (like I meant to change a color of a path or something) I can go back to inkscape and alter it there, then re-upload to the UI.
Everyone’s got a different workflow, this one works for me and feels pretty effective and efficient.
EDIT:
this brings me back to one of my common lines of thought here. Often the amount of time and effort people put in to save literally pennies of material isn’t worth it. Take proofgrade plywood. At $22 per sheet and 240 square inches per sheet, you get a price of just $0.05/square inch. If you are worried about a 1" strip down the long side of your material, you’re talking about a dollar’s worth of material. To put that into perspective, your glowforge cost thousands on dollars, all of us have spent a great deal more than that on tools and tapes and external fans and whatnot, $1 shouldn’t be a make-it-or-break-it kind of amount. Besides, your hourly rate is hopefully high enough that the time it takes to stop the loss of 20 square inches of material is simply not worth it. Your time has great value.
Note, I chose this example so that would be intentionally huge, it’s so easy to get much more accurate than 1", so my example was overly generous. So, the next time you are fiddling with layout for 25 mins, ask if you’d pay a buck to have saved that time and frustration. My answer is almost always yes.