First, you are talking about “yaml frontmatter fields” or “inlines fields”? In frontmatter (format name: value) and in inline-field (format name:: value) you can write a long paragraph (multiple lines) without problem. A paragraph is a group of a continuous sentences, without line breaks (your example isn’t a paragraph!).
Add a value as a list is possible in frontmatter fields using one of these syntax:
example: [item 1, item 2, item3]
or (attention for the two spaces before “-”)
example:
- item 1
- item 2
- item 3
Dataview can “read” an element in your text if you use an inline field. In your example you need to identify the wanted element (a sentence or a paragraph):
## Title one
summary:: Some text I want to be aggregated with multiple sentences. This is the second sentence.
## Title two
summary:: Some other text I want to be in a table.
EDIT (one extra tip):
You can ‘simulate’ multiple paragraphs if you write in continuous mode using the html tag <br> to separate paragraphs.
In this way, this…
Lorem ipsum dolor sit amet, consectetur adipiscing elit. [[Curabitur]] eu magna id est interdum euismod id at lectus. Aliquam aliquam, lectus at cursus volutpat, mi libero malesuada enim, in iaculis augue elit ut tellus. <br>Aenean dignissim lorem non urna tempus sollicitudin. Donec a est urna. <br>Ut luctus, ex non semper ultrices, justo ante malesuada diam, et `pretium` lorem augue vitae elit. *Morbi* ut bibendum **mauris**, gravida sollicitudin dolor. Nulla suscipit eget arcu sed placerat.
results in this:
Lorem ipsum dolor sit amet, consectetur adipiscing elit. [[Curabitur]] eu magna id est interdum euismod id at lectus. Aliquam aliquam, lectus at cursus volutpat, mi libero malesuada enim, in iaculis augue elit ut tellus.
Aenean dignissim lorem non urna tempus sollicitudin. Donec a est urna.
Ut luctus, ex non semper ultrices, justo ante malesuada diam, et pretium lorem augue vitae elit. Morbi ut bibendum mauris, gravida sollicitudin dolor. Nulla suscipit eget arcu sed placerat.