Is there syntax to create a defined space between paragraphs when Scrivener compiles the document from MMD --> PDF? For example, if I would want to add blank space between bullet points:
Some syntax to generate blank space of 200px or 400px or…
No it doesn’t have much by way of specific typesetting control. You would need to insert the raw LaTeX code for that, surrounded by HTML comment syntax. If you are doing this often, you may wish to make an abbreviation macro, using compiler Replacements.
[size=80]Using a custom macro to create typesetting commands: before and after.[/size]
In this example, the Replacements pane in the compiler has an entry that converts [b]<spacer>[/b] with [b]<!--\vspace{50mm}-->[/b] (I recommend using fixed units of measurement rather than pixels, as pixels are a bit technical and their real-world distance can shift depending upon the output resolution).
If you wanted to make that more powerful, you could change the Replacements with [b]<spacer:$@>[/b] to [b]<!--\vspace{$@mm}-->[/b]. That would let you type in [b]<spacer:100>[/b], in Scrivener, to add a 100mm space.
Of course, if you are just doing this once, it would make more sense to type in the code directly into the editor. 
I use \bigskip, \medskip and \smallskip in the Replacement, for big, medium and small spaces.
‘bskip’ (written in the text) => becomes in the Replacement, and a big vertical space in the pdf,
idem with:
‘mskip’ => becomes in the Replacement
‘sskip’ => becomes in the Replacement.
F.