yep, the smoothing button in the sample editor is basically a quick filter to shave off high frequencies, saves setting up an eq/filter device, or denoising plugin…but with those of course you can go more in-depth, detailed with the frequency shaving. I often use the smooth button for cymbals & hi-hats containing to much high freqs.
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 ( https://forum.renoise.com/t/new-tool-3-0-cdp-lua-tool/41466 ) 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.