afaict, there's no dedicated .sfz editor app that i know of yet. maybe there are. you always have as last resort to edit one as plain text, taking care to obey to syntax and semantic rules (ok, sorry, this is just me thinking out loud, because i know this much about the .sfz spec:)

and yes, there's a linuxsampler mailing-list and also a forum. also #linuxsampler on irc.freenode.net . i believe most of your worries are best answered by the sfz engine's author(s) hanging out there ;)

I think I vaguely remember someone posting a script to create sfz files to this list but maybe that was to create Hydrogen files? Once I have got a working sfz (I should've just downloaded a free one instead of trying to make one myself first really) then it'd be easy enough for me to write a script to automate the creation of sfzs but I'd still prefer to see such functionality integrated into qsampler, gsampler or fantasia - my philosophy being that if we want to stand a good chance of attracting non-unix geeks to Linux audio then all common tasks should be achievable without any scripting or cli voodoo.