# How can I find all of the current stylesheet notebooks?

I want to find all of the stylesheet notebooks currently open. Is there a modestly fast way to get at this?

This is somewhat slow, but it gets the job done:

AbsoluteTiming[
sDefs =
AssociationMap[
Key["StyleDefinitions"]@*Association@*NotebookInformation,
FrontEndExecute@
FrontEndObjectChildren[$FrontEnd] ]; styleNotebooks = Cases[Keys@sDefs, Alternatives @@ Flatten[DeleteCases[Values@sDefs, None]] ] ] {0.069589, {NotebookObject[Defer[$FrontEnd], 243],
NotebookObject[Defer[$FrontEnd], 83], NotebookObject[Defer[$FrontEnd], 220],
NotebookObject[Defer[$FrontEnd], 215], NotebookObject[Defer[$FrontEnd], 105],
NotebookObject[Defer[$FrontEnd], 4], NotebookObject[Defer[$FrontEnd], 5],
NotebookObject[Defer[$FrontEnd], 6], NotebookObject[Defer[$FrontEnd], 75],
NotebookObject[Defer[$FrontEnd], 81], NotebookObject[Defer[$FrontEnd], 82],
NotebookObject[Defer[$FrontEnd], 104], NotebookObject[Defer[$FrontEnd], 106],
NotebookObject[Defer[$FrontEnd], 107], NotebookObject[Defer[$FrontEnd], 186],
NotebookObject[Defer[$FrontEnd], 229], NotebookObject[Defer[$FrontEnd], 230]}}


It could be made faster if I knew how to get the NotebookInformation` to vectorize in a single call to the FE, but alas I don't.