At present, Designrr does not permit superscripts. This is a problem for several reasons, one being accessibility. Designrr Support told me that the only way to use a superscript in your document is to create it elsewhere, take a screenshot, and add that image onto a page. Again, there are multiple issues with this, but the one I'm focusing on here is accessibility. Many folks with accessibility needs - eg, older adults persons with disability or visual impairment, etc. - use a screen reader for PDFs. Screen readers typically do not convert images very well, making them difficult to read on their devices.

Even without this concern, I find it a bit ridiculous not to be able to do superscripts. It's a really basic feature of writing.