Query parameter key used to pass the serialized scroll group state main holds at the moment a
window is created, so that window's synchronous readers are right on its first render instead of
showing the default reference until a round trip returns.
Absent when main has nothing to pass — a profile that has never navigated, or one whose state is
still only in a renderer's own store awaiting its one-time handover. A renderer that does not
find it falls back to what it can read for itself, and then to the default.
Query parameter key used to pass the serialized scroll group state main holds at the moment a window is created, so that window's synchronous readers are right on its first render instead of showing the default reference until a round trip returns.
Absent when main has nothing to pass — a profile that has never navigated, or one whose state is still only in a renderer's own store awaiting its one-time handover. A renderer that does not find it falls back to what it can read for itself, and then to the default.