Insert a Unicode Sentence Break ValueA Unicode sentence break value is one of the many Unicode properties that you can insert via the Insert Token button on the Create panel.

Every Unicode code point has exactly one value for the Grapheme_Cluster_Break property. This property is part of Unicode Standard Annex 29 (UAX 29) titled “Unicode Text Segmentation”. This property is used to determine the boundaries between sentences. Such a boundary is a sentence break. The property alone does not determine where the breaks are. Rather, the rules in UAX 29 use the values that the characters before and after a position in the text have for this property to determine whether there is a sentence break at that position.
It’s not very likely that you would need to match this property with a regular expression. You could use it to implement the rules in UAX 29 using regular expressions. But most regex flavors that support this property also support \b{sb} to match an actual sentence break according to UAX 29. You can insert that with the Sentence Boundary item in the Anchor submenu of the Insert Token menu.