You can declare as many output ports as you want. For the sidechain it makes sense to have the repeatable attribute because it let the host decide how many inputs it wants to connect. But for the plugin output, I think that only the plugin can tell the host how many output it wants.

Right now the scenario would be: - plugin send CLAP_EVENT_NEW_PORTS_CONFIGS to the host - the host deactivate the plugin - the host scans the available configurations, the plugin can expose only the new one - then the host can select the new configuration and activate the plugin

What do you think of that?