notebooks - All the group formatting available in Mathematica

I was wondering how many pre-defined group formatting style there is in Mathematica. From Format -> Style, one see that we can go from Title (for Alt+1) to Subsubsection (Alt+6). However, this does not seem to be exhaustive. This is because, if I press Tab on a line created from any of those formattings (from Alt+1 to Alt+6), then I can automatically "move down one level" each time. However, from Subsubsection, it seems that I can still go 2 more levels down, after which Tab does its "normal" job. Are these 2 additional formattings somewhere to be found in some documentation? Are they in any way "special" and can I assign keyboard shortcuts for them as for the other ones?

Answer

The option StyleKeyMapping controls "Tab" and "Backspace" does to the style (AFAIK, it is not documented).

Row[Table[Most@NestWhileList["Tab" /. CurrentValue[{StyleDefinitions, #, StyleKeyMapping}]&,
     i, Not[StringMatchQ[#, "Tab"]] &] // Column[Style[#, #] & /@ #] &,
 {i, {"Chapter", "Title", "Section", "Item", "ItemParagraph", "ItemNumbered"}}], Spacer[10]]

The styles "Subsubsubsection" and "Subsubsubsubsection" are not listed in the Format >> Style menu.

The StyleKeyMapping option value for some "*section" styles are:

CurrentValue[{StyleDefinitions, "Subsection", StyleKeyMapping}]

{"Tab" -> "Subsubsection", "Backspace" -> "Section", KeyEvent["Tab", Modifiers -> {Shift}] -> "Section"}

CurrentValue[{StyleDefinitions, "Subsubsection", StyleKeyMapping}]

{"Tab" -> "Subsubsubsection", "Backspace" -> "Subsection", KeyEvent["Tab", Modifiers -> {Shift}] -> "Subsection"}

CurrentValue[{StyleDefinitions, "Subsubsubsection", StyleKeyMapping}]

{"Tab" -> "Subsubsubsubsection", "Backspace" -> "Subsubsection", KeyEvent["Tab", Modifiers -> {Shift}] -> "Subsubsection"}

To see the full style definitions, you can use

CurrentValue[{StyleDefinitions, "Subsubsubsection"}]

{CellMargins -> {{66, Inherited}, {2, 10}},

StyleKeyMapping -> {"Tab" -> "Subsubsubsubsection", "Backspace" -> "Subsubsection", KeyEvent["Tab", Modifiers -> {Shift}] -> "Subsubsection"},
CellGroupingRules -> {"SectionGrouping", 60},
PageBreakBelow -> False, LanguageCategory -> "NaturalLanguage", CounterIncrements -> "Subsubsubsection",
CounterAssignments -> {{"Subsubsubsubsection", 0}, {"Item", 0}, {"Subitem", 0}, {"Subsubitem", 0}, {"ItemNumbered", 0}, {"SubitemNumbered", 0}, {"SubsubitemNumbered", 0}}, MenuSortingValue -> None, FontFamily -> "Source Sans Pro",
FontSize -> 15, FontWeight -> "Bold",
FontColor -> RGBColor[0.778286411841001, 0.4230563820859083, 0.16115053025101092`]}

Similarly for 'Subsubsubsubsection".