I have a plugin to lock chests using a sign so only the owner can access it, with spells that break blocks, when the sign is replaced people can access and steal from the chests temporarily until the sign is fixed with the writing that locks it,

This would probably need integration with the sign plugin. Use /mexample set safe for now, that will turn of all block-breaking.

The problem is even if you prevent the plugin from breaking signs, if it breaks a block the sign is attached to, the sign will break.

if this plugin only works by attaching signs directly to chests then it could be fixed- use /meditor materials destructible and add signs to the list.

i never got this to work i did /meditor materials destructible I added signs but they still broke, I also typed indestructible and it said it worked but they still broke