Where Navigation Build Data included and saved?

There is a level named [Sample]
I did Build->Nav Build on the top menu.
And I saved that level.
But [Sample_BuiltData.Uasset] has not been created.

Nav Build is directly included in the level? not [_BuiltData.Uasset]?

If I baked Lighting first,
And Build Nav,
[_BuiltData.Uasset] was created and modified.
even if only Nav Build was changed.

That’s why my question has deepened.

Please help me.