When you say "Index" isn't that already inherited in the path sort?
No, there can be duplicates paths in Everything.
For Name sorting, the index is done last:
Explorer.exe C:\windows (Fat index)
Explorer.exe C:\windows (Filelist index)
Explorer.exe C:\windows (NTFS index)
Notepad.exe C:\windows (Fat index)
Notepad.exe C:\windows (Filelist index)
Notepad.exe C:\windows (NTFS index)
Everything can now lookup a file/folder in the index instantly with name/path.
For Path sorting, index is done first:
(Fat index) C:\windows Explorer.exe
(Fat index) C:\windows Notepad.exe
(Filelist index) C:\windows Explorer.exe
(Filelist index) C:\windows Notepad.exe
(NTFS index) C:\windows Explorer.exe
(NTFS index) C:\windows Notepad.exe
Everything can now find child instantly.
I would suggest something like ctrl+clicking a column header would "stable search" that column with whatever the existing search on screen happens to be right now, so it becomes a 1-click-solution. If you are currently sorted by Size, and you ctrl+click on Path, then Size is effectively your "secondary sort" now, and any other tertiary sorts from before that are also retained where paths & sizes match.
Shift + click already does this.
Except, it's limited to one secondary sort.
Ctrl + click would just allow additional stable sorts.
If we're loving semicolon dupe:name;size;date then maybe some other syntax like sort:name;size;date also follows?
I just tried this too! It's already on my TODO list!
Thanks for the suggestion.