It would be nice to have two buttons, one to move all Inv to Backpack, and the other Backpack to Inv.  At least all that fits, would also be nice if while moving if there were already an existing stack of something it increased/decreased it.  Just a thought.

It would make sense to implement this as a more generic plugin since it would be useful for any container, not just backpacks.

No, several mods exist that do all the containers, free and paid.  I use AbsolutSorter because I like the 'Nearby' feature.  Its paid for at ChaosCode.

Backpacks is the last to go.  Plus backpacks contents are implemented differently so that code cannot be used anyway.  (thats what I dev told me; think it was Kily0u).  So this would need to be specific to the Backpack implementation - plus I did try adding the backpack to the AbsolutSorter containers.  It did not work.

Backpacks use a generic ItemContainer object native to the game, so any logic relating to moving items between an ItemContainer and a player inventory would be compatible. The differences are likely in how the backpack being opened is detected. Simple compabitility changes can be made such as adding hooks in Backpacks or the container plugins, or by having Backpacks calling existing Oxide hooks that the container plugins already recognize. That's how this should be approached. I can't account for the specifics of how those plugins work without seeing their source, so worst case Backpacks may need to be changed real container entities. Also, the statement "Plus backpacks contents are implemented differently so that code cannot be used anyway" is misleading since the Backpack implementation can always be changed.

I use this one: Quick Sort. There is a "loot all" (and meny others!) button and it works like a sharm (for other container entities). Would be great if you could help me to get it work with backpacks.

Merged post

Got it. Works like a charm.

Added in the latest version of quick-sort plugin.