Please! It’s the only basic processing function not available in the sample editor, and it is very important
Currently there is this tool: http://tools.renoise.com/tools/phase-invert-sample
But it’s the sort of basic function that should be integrated into the sample editor.
Here is the original feature suggestion from 2004(!) https://forum.renoise.com/t/trackdsp-phase-invert/14985
Thanks