Per this thread, it's not possible to customize the text that appears when you check "Show message to prompt the user to submit another record." In this thread, a workaround is given - add your own link to the thank you screen - but the frustration with that is that it opens in a new tab rather than the same tab. Further, I'm finding that the text is a set color that does not behave according to appearance properties. Therefore, even with a default theme selected, on a dark background, the type stays dark:
It would be great to customize this text in terms of style, content, and hyperlink properties.