No.
The original source file is required for edits made with plugins like Topaz, Nik, etc. in Photoshop.
I mean, OK, truth? - it's possible, if you know what you're doing (it's not supported by Adobe/Lightroom) to edit the smart preview file with an external editor, but the changed file will be reduced resolution and quality, and it will not be possible to retrofit changes back to original when it comes back online, etc.
The option to edit externally is disabled when original is offline, even if smart preview is available - that's on purpose.
So, the answer is, for most practical purposes: no.
That said, the title of this post was "How to..", and that question I did not answer.
Also, the original post asked "Is it possible..", and the answer to that question is: yes - it is possible.
It's just that since it's not possible in a supported way (without caveats..), I said "no".
So, if you're happy with that answer, then we're done here.
(but if you want a different answer, consider re-wording the question ).
Cheers,
Rob