my guess is you'd have to build a custom image with the plugin in it. pretty sure there are docs in the polar repo on how to do this.
Discussion
Yeah, found something about it here. Seems like you have to customize Dockerfiles to do it.
https://github.com/jamaljsr/polar/blob/master/docs/custom-nodes.md
yeah it's not the most straightforward thing. i played around with trying to make a plugin for cln a long time ago and was trying to make a nice little flow to doing this but couldn't get anything i liked. it'd be interesting to mount the plugin in the image at runtime and enable the plugin using the config. that give a little better turn around time when developing. would just need to figure out a smooth way to do it.
Yeah this flow seems very janky (at best) at the moment. I think we can solve this somewhat with docker bind-mounts. It would be nice if this was something we could specify in Polar too, to make it even easier.