I made a core race, then added a sub-race. When I went to test it out, only the sub-race appeared. The sub-race was separate and did not get any of the bonuses from the core race. Nor was there any mention OF the core race or its features. 

I assumed this meant that I had mistakenly made a subrace when what I should have made was a variant. I went into my subrace, checked it off as a Variant. I went to test it again, and both my Core and Sub races were shown. But both were entirely separate. My variant still does not gain any benefits or relation to the Core Race, and you cannot select the Sub Race through clicking on the Core Race (like you would with say an elf or genasi).

Does the concept of variants and subraces work differently for Homebrew than it does for classic content?

Regardless; Am I to throw away this entire concept, and instead simply make a handful of nearly identical core races that have most of the descriptor text copy and pasted?

Once a sub or variant is added the base race is no longer a choice (like you can’t be just an Elf). But since there’s no “Race Group” for your race there’s no way to make them nest. The current convention is to name them as “[Race], [Subrace]” so they group alphabetically.

Thank you so much for the help! Does this mean that, effectively, there is no reason to create subraces or variants for Homebrew races?

By this I mean, if I have to add in all the lore, class features, modifiers, spells, etc. in again anyway, am I wasting my time by adding in races as subraces/variants instead of their own stand-alone races?

You do not need to add any of that in again at all, just make sure the “Is Called Out” checkbox is checked and those traits will be visible for all subraces & variants.

I suppose what I'm asking is if it's just adding more work on to create sub races and variants, when sub-races appear to delete the core race, and variants don't appear to save any of the information of the core race itself.

Quote from Calamina >>

I suppose what I'm asking is if it's just adding more work on to create sub races and variants, when sub-races appear to delete the core race, and variants don't appear to save any of the information of the core race itself.

 
You do whatever you want, but the answer is “no.”

Subraces don’t “delete” the parent race. The parent race is simply not selectable is all. (Like you cannot actually select “elf,” you have to select a subrace to play.) The parent race features apply to all subraces, the Subrace features add on to those parent race features. It is Les work to make one race and three subraces for it than it is to recreate the entire race multiple times.

The variant races also retain all parent race traits and only replace the traits selected with the variant traits.

The only issue you’re struggling with is the fact that the parent race is not displayed, but if you make those traits “Is Called Out” then they will display in the builder.

Here, “Subclasses & Races” #5: (https://www.dndbeyond.com/forums/dungeons-dragons-discussion/homebrew-house-rules/131411-a-homebrewers-how-to-faq). If you follow the naming convention recommended there it’ll look better and if you make sure the base race features are “called out” then it’ll work as well as anyone else’s homebrewed race.

But again, like I said, if you wanna do it the longer, harder way just for the visuals then go right ahead.

You can always recreate the core race as a variant or subrace, that way it will show up next to your other races, You would only need to really copy the discription, and traits that are "invisable" like age or size. aslong as its clear in the discription that these subraces are all related somehow, this is a much easier way of having them all having the same backbone with some minor tweaks.

Sorry for poor grammar and english, It is my native language, but as a native of the british isle, I am DRUNK! *laughs in Bardish*

DID NOT NOTICE HOW LATE I AM! HA!