Justification of text is a paragraph formatting attribute. You can't change the justification of less than a paragraph. You can change interparagraph line spacing (space before/after) so that it looks no different from the line spacing within a paragraph.

You can use distributed text (Ctrl-Shift-J) to stretch text between paragraph indents.
Alignment / Justification of Text in Microsoft Word

Distributed text treats everything in a line including spaces and punctuation as a character. Note, the justification is between paragraph indents, not between margins.

Fine-tuning of the appearance of text throughout a manuscript is best done by use of Styles to maintain consistency.