もやもや can mean a range of feelings from:
Gloomy
Annoyed
Uneasy
Or any feeling where something "doesn't sit right".

Depending on the connotation, this can be as broad as meaning, "the many things we are uncomfortable with" to something very literal like referring to a collection of tragic stories that have been compiled into a book.

In your example link, it seems to be more like the former and referring to multiple aspects or topics that someone may need consultation on in order to feel more comfortable moving forward. That people want to start a business but are unsure how to move forward. These things that they are unsure what the best practices are are the モヤモヤ編

Since you are directly saying that it is not something where unknown or uncertain applies as a definition, it may be more referring to the miscellaneous annoying aspects involved in a process?

Hopefully the references I linked help contextualize it a little in your text's case.

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Note added at 3 hrs (2020-05-19 23:22:29 GMT)
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My apologies, that first link doesn't apply, it was the other reference from a different question I answered about モヤモヤ last year.

It's hard to be sure about my answer when I haven't seen the original sentence.
I think the person holding the event is really trying to address potential entrepreneurs' common concerns (or worries).

モ ヤ モ ヤ is an expression. The meaning depends on the context in question. But major meaning of モ ヤ モ ヤ is "ambiguous" or "confused". So this depends on the context of the conversation.