The Import Formats give complicated choices that took me ages to understand! (maybe still don't.:) )
Expecially the formats that contain a forward slash.
I suggest you read this blog article that can give more information than I can give here.
https://www.lightroomqueen.com/import-create-dated-folders/
I mostly prefer to use the "20190922" format (no slashes and 'Into subfolder' not ticked) as it gives me full control over exactly where I want to put my files. Thus if I highlight 2019 in the Destination panel I get a sub-folder 20190922 with the contained imported files.
This format might suit you as you can define {2019/09/Misc/sub} exactly as you want.
As an example I see this screen-clip with the settings shown-
