You can also do:
(empty line)
\
(tab)
(tab)
Each empty line with a tab will create an empty line in preview. the \ symbol won‘t be shown in preview.
Extra bonus: If you want to avoid the empty lines getting “swallowed” by folding an above header, do this:
# .
\
(tab)
(tab)
The amount of hashtags should be equal to the above header. Instead of a . you can also use another symbol, but I found the dot to be least obtrusive.