I've created a new Wolfram Language Package notebook from Mathematica V12.1.1 running on a Mac.

I want to set line indenting to a value of, say, 2 for expression formatting for the whole notebook. using the Option Inspector, this works on a cell by cell basis, but not for the selected notebook or globally.

Also, unlike ordinary notebooks, the "Edit Stylesheet" menu is disabled in package notebooks.

Is anyone able to give me a pointer as to how I can set line indenting for all code cells so I don't have to set the value individually for every single cell.

EDIT: I've just noticed that if I save and re-open the package notebook, my cell-by-cell indentations are forgotten.

Thanks in anticipation...