Here is one I use often.
It was mostly developed by @AntoniDol and @SWM (thanks again) – and me somewhat.
Stage name: (The almighty) Paragraph Exploder . 
I use it to “explode” paragraphs into their sentences (each sentence technically becoming a paragraph) when I want to do some deep editing of a text in printout. (Say I want room to scribble, or be able to freely reorder sentences, etc.)
It marks the sentences at their beginning and/or end, depending on if a said sentence was previously connected to another sentence in the context of a paragraph. Thus giving a visual cue as to what is – and what isn’t – in fact altogether a paragraph, as well as allowing to quickly rebuild the paragraphs, through a later Project Replace operation.
The formula (RegEx → Uncheck “Ignore Case”) :
Replace
([\?\!\.\…])\s([A-Z])
With
$1•
•$2
Result:
To later reassemble the paragraphs, replace 
with a space.
(No RegEx this time. Just a normal replace.)
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Though unlikely (it is not the same one as the lists’), first make sure you don’t somehow have the dot symbol already in use in your project.
Use any other “special” character/symbol if needed. Which one doesn’t matter, as long as it is searchable and exclusive to this operation.
. . . . . . . . . . .
Before/After screenshots
