I haven't used D standard, but it looks like regular EADGBD tuned a whole step down. So you could basically use that tuning on the site and just select the key

I haven't used D standard, but it looks like regular EADGBD tuned a whole step down. So you could basically use that tuning on the site and just select the key a whole step below what you want, and it will align on your fretboard properly, as a workaround.