There does not seem to be a denoiser for audio integrated into kdenlive yet - am I right?

If so (please give me some feedback on this), I should file a feature request accordingly.

Kind regards.

SoX has a noisered effect, but it requires a profile generated using noisered, which may be difficult to integrate.

Do you know of a LADSPA filter that will do this?

Sorry, I don't. But how about taking out the corresponding part from the open source software "Audacity" and just integrating it?