Is there any feature to monitor a folder for new files?

Yes, eyes, and maybe brain cooperating at the same time. You get the message to your brain if you have downloaded something and then you can go and add it to your favourite player...

Seriously, no.

I believe that the foo playlist tree does something like that, but I haven't tried it so I'm not sure. Also, my understanding is that it's still officially considered an unstable plugin by foobar's programmer and the foobar community. Check the thread for more info.

Just because it was mentioned, I'll try to be more specific.

You're looking for the $drop feature in playlist tree. You can ask for more informations here, files are here, a basic tutorial for the plugin is here.

Warning: the component is still listed in the known problematic component list.

Thanks for the clarification, marcomk. I knew it was possible, but as I said I haven't used the component.

Look in the core database settings.

You can rescan database directories for new files.