Learning Curve is so steep, to level it, you need to invest lost of efforts

[Jerware]

@tjp

This is common is other development environments like Web Development... anything with a package/library management platform. But as @Moors7 said, if it's for personal or project use only. Just use the + to add the files.

I appreciate the pointer to the + symbol, but it's impractical for libraries with a large number of source files like the two I stated in my first post.

@tjp

Simply not true. Take a look at [My Project][1]. I compile that in Particle Dev without modification. The key is knowing that the file structure gets flattened, not that it needs to be flat from the start. That means that #include statements don't need the subfolder name, simply the file name.
[1]:GitHub - tjpeden/mane-avis: Photon-based smart alarm clock

Ah! This is very useful information that is not stated in the docs (as far as I can tell). It's still not ideal, but it's much friendlier than putting all files in the same directory. Thank you for pointing it out. I've already reconfigured my project.