Hi Luis,
The jars from the GeoServer extension should be stored in the resources folder, and override the files from the geoserver container like this:
geoserver:
image: georchestra/geoserver:${GEORCHESTRA_VERSION}
depends_on:
- ldap
volumes:
- ./config:/etc/georchestra
- /home/geo/volumes/geoserver/datadir:/mnt/geoserver_datadir
- /home/geo/volumes/geoserver/geodata:/mnt/geoserver_geodata
- /home/geo/volumes/geoserver/tiles:/mnt/geoserver_tiles
- /home/geo/volumes/geoserver/native_libs:/mnt/geoserver_native_libs
# extension
- ./resources/geoserver/extensions/metadata/XXXX1.jar:/var/lib/jetty/webapps/geoserver/WEB-INF/lib/XXXX1.jar
- ./resources/geoserver/extensions/metadata/XXXX2.jar:/var/lib/jetty/webapps/geoserver/WEB-INF/lib/XXXX2.jar
- ./resources/geoserver/extensions/metadata/XXXX3.jar:/var/lib/jetty/webapps/geoserver/WEB-INF/lib/XXXX3.jar
....
Hope this helps,
F.