The README instructions say "the include section" and then show a JSON sample that uses the key includes.

To use a plugin, add the following reference to the include section of your devbox.json file.

"includes": [
    "github:jetpack-io/devbox-plugins?dir=<plugin-name>"
],

My devbox version is 0.9.1

According to the README.md documents in each plugin the plugins should be writing to:

• devbox.d/<plugin-name>/conf.d/
• .devbox/virtenv/<plugin-name>/process-compose.yaml

Instead the plugins are writing files to:

• devbox.d/jetpack-io-devbox-plugins/conf.d/
• .devbox/virtenv/jetpack-io-devbox-plugins/process-compose.yaml

This has the side effect that if multiple plugins are being used then files with the same name, like process-compose.yaml,
are being overwritten by what ever is defined last.

For example:

  "include": [
    "github:jetpack-io/devbox-plugins?dir=rabbitmq",
    "github:jetpack-io/devbox-plugins?dir=mongodb",
  ],

Results in .devbox/virtenv/jetpack-io-devbox-plugins/process-compose.yaml containing

version: "0.5"

processes:
  mongodb:
    command: "mongod --config=$MONGODB_CONFIG --dbpath=$MONGODB_DATA --bind_ip_all"
    availability:
      restart: on_failure
      max_restarts: 5

And if I swap the order of the plugins:

  "include": [
    "github:jetpack-io/devbox-plugins?dir=mongodb",
    "github:jetpack-io/devbox-plugins?dir=rabbitmq",
  ],

Results in .devbox/virtenv/jetpack-io-devbox-plugins/process-compose.yaml containing:

version: "0.5"

processes:
  rabbitmq:
    command: "rabbitmq-server"
    availability:
      restart: on_failure
      max_restarts: 5
    daemon: true
    shutdown:
      command: "rabbitmqctl shutdown"
  rabbitmq-logs:
    command: "tail -f $RABBITMQ_LOG_BASE/$RABBITMQ_NODENAME@$(hostname -s).log"
    availability:
      restart: "always"