Edit: OK i feel like an idiot MCA Selector had the exact same issue with not rendering chunks but trying to delete the unrendered chunks with it worked as I wanted it to.
Hi, I've generated an amplified world in 1.14 and have been playing on it since.
However, with the latest update I am looking to delete the chunks around my base to generate the new ones nearby, as I've since grew to regret my amplified decision (terrain looks amazing but it's a nightmare to navigate, and I want to experience the new terrain unmodified for the time being). The generation type is an issue I have resolved, as I've used NBT Explorer to change it.
The real problem though is deleting the chunks. As you can tell from the screenshot I can only see a few chunks (which I think were generated in 1.17 or 1.18).
What you see in red is the chunks I am interested in (generated way back then, as they are the spawn chunks AND the nearby ones), but for some reason I can not get them to show up. The doozy is that the same happens even in a freshly generated 1.18 world, which eliminated it being a 1.18 issue (and also the fact that those chunks were pre-1.18 anyway)