I recognize four kinds of poetic flow-breaks, but I'm sure others will find more. My four are: (1) the orthodox line-break, (2) the variable indentation, (3) the interior line-gap, and (4) the intra-syllabic line-break.

Any poetic flow-break can be empty or filled--with asterisks, say, or any other kind of symbol (or spoken sound) without a clear punctuational or other semantic use.

The Orthodox Line-Break

The line-break is simply (and conventionally) any space or other block of asemantic fill that prevents a line from reaching some pre-set (loosely or precisely defined), repeating margin to the right.

The Variable Indentation

The variable indentation is any space or other block of asemantic fill that prevents a line from starting at some pre-set (loosely or precisely defined), repeating margin to the left. It is the same as a line-break except at the opposite end of a line. The Interior Line-Gap

In written poetry, an interior line-gap is simply a block of two or more spaces or other asemantic matter within a line, spoken or written.

In oral poetry, interior line-gaps--and the other poetic flow-breaks, as well--are pauses keeping the speaker from continuing automatically to some pre-set stopping or starting point, such as a period, or the capital letter at the beginning of a sentence.

The Intra-Syllabic Line-Break

The fourth of my poetic flow-breaks, the intra-syllabic line-break, is confined to written poetry. Like the orthodox line-break, it occurs at the end of a line; unlike the latter, however, it can end at a pre-set margin; it interrupts flow by stopping a line in the middle of a syllable (generally but not necessarily always, without a hyphen), as in the following sentence. My i
mpression is that E.E. Cummings invented this devi
ce. Certainly he was among its first significant users. Prose contains poetic flow-breaks, but they are few, and predictable: the paragraphs of prose works generally begin and end with variable indentations, for instance. And interior indentations using dots are used in prose to indicate ellipses. Poetry uses the poetic flow-break several magnitudes of order more frequently and consequentially than prose does.