Storage No Poof (SNP)

This mod saves the items stored in container blocks from removed mods. When such a block is missing, it is replaced with a special block that drops all of its stored items when broken. If the container held a large number of items and you want to avoid possible server lag, you can remove the items manually; once it is empty, the block destroys itself automatically.

At the moment, preservation works only for mods that store their inventory in a top-level Items tag, which is also the format used by vanilla containers. Support for custom rules, allowing modpacks to preserve items from specific tags and inventories, is planned for a future update.