I realize that this is a little premature in that you haven't released it yet, but InkscapePortable 0.92.3 leaves a fontconfig folder in AppData — %appdata%\Local\fontconfig\cache which contains two files, CACHEDIR.TAG and d031bbba323fd9e5b47e0ee5a0353f11-i686.cache-7.
This is the portable version available on Inkscape's site ( https://inkscape.org/en/release/0.92.3/windows/32-bit/portable-app/dl/ ) which is in PAF format and was uploaded by Gord Caswell, so I assume it's the same one you will eventually be releasing.
This was first reported at https://www.portablefreeware.com/forums/viewtopic.php?t=3927&p=89398#p89398 . I confirmed that it happens on my computer (Win7 Pro SP1).
Thanks for catching that. I've fixed it locally, and we'll upload a new build prior to the official release announcement by either Inkscape or PortableApps.com
This is fixed in Inkscape Portable 0.92.3
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