from this thread, there are tools that work in Renoises sample editor;https://forum.renoise.com/t/denoising-noisy-synths/42110
If you didn’t know, there is also this script which uses the sox application for denoising;
https://forum.renoise.com/t/new-tool-2-8-noise-reduction/36480
The CDP tool ( http://www.renoise.com/tools/cdp-interface ) has a bunch of denoising processes in ’ Specnu - Specnu Clean’ using so called noisefiles…a noisefile is the 2nd sound you set up in the tool gui and will be subtracted from another sound. So if you have a recording of a synth as one sound, and portion of the noise audio as second, you can remove the noise content from the synth.