The list of plugins can be viewed as follows:
cd /app/code
./nodebb plugins

Plugins can sometimes make NodeBB not start up.

To fix this, first put the app in recovery mode (Dashboard-App settings-Tab: Repair).

Then, open a Web Terminal:
cd /app/code
/app/pkg/start.sh # this create and configures nodebb
./nodebb reset -p nodebb-plugin-pluginname