Hi w.patrick.gale! I've forwarded your feedback on to the team that owns the API documentation. For completed responses, they are under the section: Survey Responses

• https://api.qualtrics.com/api-reference/reference/singleResponses.json/paths/~1surveys~1%7BsurveyId%7D~1responses~1%7BresponseId%7D/delete


• https://api.qualtrics.com/api-reference/reference/singleResponses.json/paths/~1responses~1%7BresponseId%7D/put

• https://api.qualtrics.com/api-reference/reference/sessions.json/paths/~1surveys~1%7BsurveyId%7D~1sessions~1%7BsessionId%7D/post


• https://api.qualtrics.com/api-reference/reference/sessions.json/paths/~1surveys~1%7BsurveyId%7D~1sessions~1%7BsessionId%7D/delete

I finally found a link to the response delete API reference here:
{"embed-error": true}I have no idea how I found it. There is no longer a navigation tree to find things on this site. (Ugggh, when I paste the URL into this submission field it gets converted to a 'Request failed with status code 500'...see attached screenshot). Here is the URL to the API reference:
https://api.qualtrics.com/guides/reference/singleResponses.json/paths/~1surveys~1%7BsurveyId%7D~1responses~1%7BresponseId%7D/delete
The API site needs a 'Feedback' feature like this one.

The new API site is really difficult to navigate the left menu pane. If you open a page the left pane does NOT show its scrollbar unless you happen to know it exists and you hover over it to make it appear. If you go to https://api.qualtrics.com/guides/reference/singleResponses.json/paths/~1surveys~1%7BsurveyId%7D~1responses~1%7BresponseId%7D/delete
for example, the highlighted left nav section doesn't even appear unless you scroll down the left nav, which seems rather silly. The behavior of the left nav scrolling is horrible, to put it lightly.
The search function also misses the mark. If you search for 'Delete a Survey Response' for instance, it doesn't even come close (see below).