I’m a newly minted slime mold enthusiast, and I’m struggling with this, too.
I’ve begun bringing samples home with me from the woods in hopes that they’ll develop into something recognizable. I’ve had mixed results, so far.
I joined the Slime Mold Identification & Appreciation group on Facebook and getting to look at lots of posts every day has been educational. I’ve posted photos a few times and gotten suggestions, too.
One of that group’s administrators, Peta McDonald, has put together a
dichotomous identification key and I’m optimistic that it will help once I get a microscope.
Best wishes!