Sorry, to be clear, in the two scenarios I mention above, neither of the following links were added to the parent page.
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/summernote/dist/summernote-bs4.min.css" />
<script src="https://cdn.jsdelivr.net/npm/summernote/dist/summernote-bs4.min.js"></script>
Only when I created a new single php page and added the Summernote Component did all 4 links get added.
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/summernote/dist/summernote-bs4.min.css" />
<script src="https://cdn.jsdelivr.net/npm/summernote/dist/summernote-bs4.min.js"></script>
<script src="../dmxAppConnect/dmxSummernote/dmxSummernote.js" defer=""></script>
<script src="../dmxAppConnect/dmxSummernoteFileUpload/summernote-upload.js" defer=""></script>
I then copied these to the parent page and all was OK.
Hope that makes sense.