So, I've not worked with this before, but from the GeoNode documentation , they describe that GeoExplorer is basically the stock out-of-the--box implementation of the OpenGEO SDK suite:
The GeoExplorer app is based on GeoExt, OpenLayers and ExtJS.
GeoExplorer is the reference implementation of the OpenGeo Suite SDK
which is based on GXP. GeoNode treats GeoExplorer as an external
module that is used out of the box in GeoNode, but it is possible for
you to create your own Suite SDK app and integrate it with GeoNode.
So I think that you can use the OpenGeo Suite Boundless SDK as your API for creating a plugin that does what you want. Here is documentation on creating plugins with the Boundless SDK:
Creating application plugins
Again, this is not a complete answer, but hopefully would give you some place to start investigating.