www.wysiwygwebbuilder.com

I understand Wysiwyg Web Builder v20 has built-in support for GLightbox. I have v21 and I've looked at the Page Property options and can't find it? All I have are:
-fancybox
-magnificpopup
-lightgallery
-pretty photo

Has it been removed again?

Did you install GLightbox?
https://www.wysiwygwebbuilder.com/free_extras.html

In WB21, lightboxes add-ons should be installed in the system folder.
Documents\WYSIWYG Web Builder\system\lightbox\<lightboxname>

No, because the v20 blurb said it was fully integrated, so I assumed that meant it was already included.

Clearly your question means that's not the case and I have to download it to integrate it.

Thanks for your response.

Installed and working - thanks again.

Now to decide whether I prefer it over the standard fancybox...

Please note that Fancybox is outdated and has not been the default lightbox for many years. In version 21, the default lightbox is 'LightGallery'.

For more information, see:
https://wysiwygwebbuilder.com/lightboxgallery.html

Sorry, yes, lightgallery

Actually, I just noticed, that despite the page default being lightgallery, and the available settings being for a lightgallery, my images are opening up as fancybox (with wide white borders and no reflection of the settings I've made). I have no idea why!?!?!

Maybe you have set the lightbox of the image itself to fancybox?

Note: if you need help then please share a demo project. The software has thousands of options and millions of possible combinations.
It's impossible to guess which combination of settings you have used

See also the forum rules.