I cannot duplicate your results. Panorama already is built to understand the format “01-May-2019”, it automatically detects that the middle part of the date is a month name and adjusts accordingly. It doesn’t matter what your date pattern is or what region you have your date setting configured for in System Preferences. I just did some testing to verify that this works, and it worked perfectly for me. I could convert a text field to date, enter dates in this format with the keyboard, and import data into a date field in this format. In all cases it automatically recognized the format and correctly brought in the date. In fact, it even worked if I quoted the date as you did in your post (I assume you put in quotes just as punctuation, but thought I’d try it just in case – and it worked).
So … there must be some additional detail you are not sharing with us that is tripping Panorama up.