As @Luligabi1 suggested, we can use the upcoming common tag for shields, c:shields, to implement a config in ModMenu for people to toggle between:

1. Disabling a shield disables only that type of shield in the inventory and nearby chests to disable for that person (how vanilla shields work)
2. Disabling a shield disables all other shields in the inventory and nearby chests to disable for that person (how vanilla shields work)

We do have to wait until the common tag is added to the Fabric API to do so, so for now it is just a reminder/ a place to brainstorm this idea.
Link to track addition of command tag to Fabric API: FabricMC/fabric#2727

Well I mean disabling that specific shield would also disable copies of that shield in chests she disabling system goes by the type of item, but yeah I'll add a config option for that.

I should reword setting one:

1. Disabling a shield disables only that type of shield in the inventory and nearby chests to disable for that person (how vanilla shields work)

This update to the FabricAPI was marked as "Likely candidate for future releases", so I think we may be able to implement this feature in the near future, and probably into 1.6.2.

The common shield tag is now in the newest FabricAPI release, 0.69.0+1.19.3, so we can add this feature now. I'll do it.

added in #112