Describe the solution you'd like
When you have an item in your main hand and your offhand and you try to salvage the item in your mainhand, it also tries to salvage the item in your offhand.

Why is this feature needed
Salvaging items in the offhand should probably just be disabled entirely. It is a small QoL at best, and ripe with opportunity for accidental salvaging. If a player wants to salvage something they should have to intentionally put it in their main hand, crouch, and right click the smithing table. That way there are some safe guards from players losing their possibly valuable items unintentionally.

Describe alternatives you've considered
Coach all players on the server how it works and hope they listen!