So this is a pretty obscure question I couldn't find an answer to.
So there's this neat program called QtTabBar, and I want to install this "portable" meaning no admin rights/permament footprint. Extracting the msi it has a bunch of dll files which I'm guessing would end up in system32, as this program effects explorer.exe. I can't put the dll's in there, but is there somewhere in windows that it will search for local user files/dlls and read them the same as if they were in system32? (somewhere in appdata if I had to guess).
e.g. if such a place existed at %appdata%\Microsoft\Windows\DLL\ then I'd put the DLLs in there and it would use them as if they were in system32.
This sort of thing can never be portable, because it will always require local registration; Explorer doesn't blindly load dlls in a specific location- it loads registered browser helper objects and shell extensions. These are in the registry.
In the case of qttabbar, it also registers in the global assembly cache, as it's written in .NET. (which is weird because .NET assemblies are well known for being completely unreliable when used as a shell extension...)