Thanks so much. Although if I don’t use media import on a post ID, then the image ends up at SITEURL/FILENAME which then ends up as a 404, the thumbnail shows, but clicking on it is 404.
However this is good enough because now I know to use “gallery ids” as post_content and won’t have to fiddle around with dates or paths.
I played around with “gallery option” and removed the link with “gallery link=”none”” and changed the size, but size wouldn’t change (even with “full”) until I added a column of 1, yet the size was still limited to the page width of the theme, fine for now.
[gallery ids="298" gallery size="full" gallery link="nonolumns="1"]columns="1"]