Trying to get this plugin: https://umod.org/plugins/sort-button work with backpacks and I thought maybe it's better to add an option in config file?
Something like

  "Sort items on save (true/false)": true,​

or

  "Sort items on save by (type/name/none)": "type",

What does "on save" mean in this context?

On saving backpack or when backpack is saved

backpack.SaveData()​

I'm not sure sorting on save is a good idea. For one, doing it with a config value would make it apply to all players, whereas players are likely to have different preferences around sorting. Some will want no sorting, some will want auto sorting, and different players will want different types of sorting.

Also, what are your thoughts on how the integration will work? Will the sorting plugin listen for backpack hooks, or do you want the backpacks plugin to be aware of the sorting plugin?

Yeah, you are right, every player can have different desires about this, but at least server admin can set the sort behavior like he think will be right, or like majority of his players prefers. It can be disabled by default and no problems.
About integration - of course the sorting plugin should listen for backpack hooks.

I agree that in some cases, with some plugins, allowing the server administrators to set a default makes sense, but sorting is so preferential that I think it should just be player-defined, presumably using the sorting UI, like something the player can toggle on/off or customize with a button. This sort of thing should probably be permission gated as well.

The idea of this request is to give admins the ability to activate automated sort of all backpacks. You can leave this option disabled by default and no one will hurts. It's just an option, that can be toggled. If admin don't want to toggle it - no problems, but if he want to switch it on - at this moment he just can't do that. I agree that this is something very preferential, but I guess some admins just can toggle it on and not give players much of choice. Are we on admins side with this, or on players side? xD

However, I added support for backpacks into sort-button. Claim request sent, waiting for response to merge my commit.
If you think you still don't want to add this option, please, just close this request (like "No thanks" or whatever).
Thanks.