I turned on Restricted Mode, and I used the core plugin “Page Preview”, and I set as the image shows.
I insert a link in Callout like these images.
When I move to the link without “Ctrl”, It shouldn’t show the Preview result.
And I can preview when I click “Ctrl”.
It shows Preview Result whether I click “Ctrl”, which means I always can preview the content when I move to the link, but it’s not what I really need.
Default Theme with CSS