The wiki page
https://github.com/GoldenCheetah/GoldenCheetah/wiki/HRV#importing-and-processing-r-r-data-in-goldencheetah
mentions that it is possible to import R-R data files in text format
into GC, but I cannot find where this is possible.
I have the same question and have downloaded my .txt file that have my HRV data. Both the methods you've listed above are for activities. The .txt files are not activities they are .txt files containing HRV. data.
I would like to be able to down load this hrv data in .txt form to GC. Is there a way to do this.