Focus on One Idea at a Time

sentence
noun | sen·tence | \ˈsen-tən(t)s, -tənz\
a group of words that expresses a statement, question, command, or wish
— Merriam Webster Dictionary

Focus Mode lets you craft your documents with care, one sentence at a time. This allows you to focus at one statement at a time.

paragraph
noun | par·a·graph | \ˈper-ə-ˌgraf, ˈpa-rə-\
a part of a piece of writing that usually deals with one subject, that begins on a new line, and that is made up of one or more sentences
— Merriam Webster Dictionary

New in iA Writer 3.1.3, Focus Mode can expand to the bounds of the current paragraph enabling you to concentrate on one idea at a time.

The above tip works on iOS and Mac