Hide useful salvage
I think this is a Known issue and happens with other warnings too. I don't think there is a work-around so you'll have to suffer it for now till they fix it. Least you won't delete/sell salvage you need in the mean time
The above is only my opinion, please don't hate me for it

SG: Suicidal Maniacs @Aurealis
GhostRaptor: Server populations have been trending upwards since Issue 13 release. There are no current plans for any server mergers and we're looking forward to Issue 14 and the rest of the year.
Yes, this warning and the 'large auction house fee' warning never stick for me. No matter that I've enabled to hide them, I get asked every time any way. Keep /bugging it.
@Liz!
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Agreed-totally irritating bug. Bug the living eff outta it. :^)
Basically too many 50's to count, but I'm generally a brute/scrapper/tank kind of guy.
Enable hide useful salvage refuses to stay turned on no matter how many times I turn it on and hit apply now. The very next time I start to sell something called for in one of my recipes the warning pops back up. Most annoying.