The plugin manager's operations are based on GroIMP commands. Thus, usable without using the GUI (neither the Plugin Manager nor GroIMP GUI are required). The list of commands is :

Exporting the list of currently installed plugins. This create a file with the list of plugin and their version installed. - complete path: /pluginmanager/commands/file/exportPlugins. Importing a list of plugins. The plugin manager will install a list of plugins provided by file containing the plugin id and version - complete path: /pluginmanager/commands/file/importPlugins. Reload the plugin repositories. This refresh the list of available plugins - complete path: /pluginmanager/commands/data/reloadRepo. Clear the cache. This delete all cached data of both plugin, and repositories - complete path: /pluginmanager/commands/data/clearCache.

it is possilbe to install plugins without opening GroIMP by using the following commands:

#install
java -jar core.jar --headless -- -cmd /pluginmanager/commands/installCMD=de.grogra.gltf;de.grogra.cli

#uninstall
java -jar core.jar --headless -- -cmd /pluginmanager/commands/uninstallCMD=de.grogra.gltf;de.grogra.cli

#disable
java -jar core.jar --headless -- -cmd /pluginmanager/commands/disableCMD=de.grogra.gltf;de.grogra.cli