Return to Answer

• obj as far as I can tell is a NotebookObject, CellObject, or BoxObject, but you can also get the current spec from from FE`Evaluate@FEPrivate`Self[]
• The id searches for BoxID->id. It can also be FE`Parent[id]. I don't know what that does.
• The offset should look like FE`BoxChild[n] or FE`BoxParent[n].
• The only SearchStart I've seen used is "StartFromBeginning".

• obj as far as I can tell is a NotebookObject, CellObject, or BoxObject, but you can also get the current spec from from FE`Evaluate@FEPrivate`Self[]
• The id searches for BoxID->id. It can also be FE`Parent[id]. I don't know what that does.
• The offset should look like FE`BoxChild[n] or FE`BoxParent[n].
• The only SearchStart values I've seen are "StartFromBeginning" and "StartFromFirstDockedCell".

##Cell Groups

###SetCellGroupOpen

In the "FEPrivate`" context. Allows one to set the open/close state of a cell group. Called like:

MathLink`CallFrontEnd@ FrontEnd`Value@ FEPrivate`SetCellGroupOpen[ cell, Open|Close|True|False ] 

Open/True and Close/False are the same thing.

Any other spec will return $Failed (which prevents it from being used to set up Dynamic open/closers)

FrontEndExecute@ FrontEnd`AttachCell[obj: (_CellObject | _BoxObject | _NotebookObject), cellExpr_, { radialDistanceFromAnchor: (_Integer | _Scaled | InlineContents), alignment: {Center | Left | Right, Center | Bottom | Top } | "EndOfContents" }, anchor: { Center | Left | Right | _Scaled | _Integer | _Real | Baseline, Center | Bottom | Top | _Scaled | _Integer | _Real | Baseline }, "ClosingActions"-> { ( "ParentChanged" | "EvaluatorQuit" | "OutsideMouseClick" | "SelectionDeparture" | "MouseExit"| "CellGroupOpened"| "CellGroupClosed" ) ... } ] 

FrontEndExecute@ FrontEnd`AttachCell[obj: (_CellObject | _BoxObject | _NotebookObject), cellExpr_, { radialDistanceFromAnchor: (_Integer | _Scaled | "InlineContents"), alignment: {Center | Left | Right, Center | Bottom | Top } | "EndOfContents" }, anchor: { Center | Left | Right | _Scaled | _Integer | _Real | Baseline, Center | Bottom | Top | _Scaled | _Integer | _Real | Baseline }, "ClosingActions"-> { ( "ParentChanged" | "EvaluatorQuit" | "OutsideMouseClick" | "SelectionDeparture" | "MouseExit"| "CellGroupOpened"| "CellGroupClosed" ) ... } ]