After reading rcollyer's post I'm still not able to understand how grouping rules work.
Here is a problem I'm facing. What I want is to create a new title, section and subsection styles. I want the title to group everything below till the next title. The section should group everything below till the next section. To see what I mean, open up a new notebook. Go to Format > Edit Stylesheet....
On this stylesheet make a new cell. Then select this cell and go to Cell > Show Expression.
Here enter the following:
Cell[StyleData["MyTitle"],
CellGroupingRules->{"MyTitleGrouping", 0},
CounterIncrements->"MyTitle",
CounterAssignments->{{"MySection", 0}, {"MySubsection", 0}},
FontSize->26,
]
Once this has been entered now go to Cell > Show Expression to revert back. Let us create two more cells in the same fashion, one for the section and subsection.
Cell[StyleData["MySection"],
CellGroupingRules->{"MyTitleGrouping", 10},
CounterIncrements->"MySection",
CounterAssignments->{{"MySubsection", 0}},
CellFrameLabels->{{
Cell[
TextData[
CounterBox["MySection"], " -"], CellBaseline -> Baseline], Inherited}, {
Inherited, Inherited}},
FontSize->20,
]
Finally, the subsection:
Cell[StyleData["MySubsection"],
CellGroupingRules->{"MyTitleGrouping", 20},
CellFrameLabels->{{
Cell[
TextData[
CounterBox["MySection"], ".",
CounterBox["MySubsection"], " -"], CellBaseline -> Baseline],
Inherited}, {Inherited, Inherited}},
CounterIncrements->"MySubsection",
FontSize->16,
]
After creating those new styles, now we can use them, here is a screenshot of what I obtained if I use the "MyTitle", "MySection" and "MySubsection" styles.

Don't mind the text I entered there. The main point here is that there is no grouping.
How can I make it behave as the regular "Title", "Section" and "Subsection" styles?


"InputGrouping"and"OutputGrouping"are obvious, but"GroupTogetherGrouping"and"GroupTogetherNestedGrouping"? Not a clue there. – rcollyer May 25 '12 at 02:53GroupTogetherGroupingis used when you want to do manual grouping. For instance, if you create two input cells in a new notebook and then you go toCell > Grouping > Group Cells/Group Togetherthen you'll see that grouping. Just look at the expression of each cell by going toCell > Show Expression. You will see that one there. I'm not sure how to make the other one show up though. Could be when you have a two title cells maybe? since you have nested groups inside a title cell. – jmlopez May 25 '12 at 02:59GroupTogetherNestedGroupingis just how"Item*"cells group together, that is, anything tagged withGroupTogetherNestedGroupingwill either group in the same group as a previous cell withGroupTogetherNestedGroupingset and the same second value, as a subgroup if the second value is larger than that of the previous, and no grouping if it's larger. It seemsGroupTogetherGroupingwill only group with cells with the same second value (or none), hence the lack of"Nested". – b3m2a1 Dec 09 '16 at 08:12Listto contain all the arguments of theTextData. Once that's done, they can be used to create the screenshot. – rcollyer Apr 26 '20 at 16:45