Normally, WordPress (and almost all themes, including Weaver Xtreme) do not typically support “double spacing”within a normal paragraph in either the classic or block editor. Weaver Xtreme supports setting line spacing (space between lines) for the whole page/post, but not for specific paragraphs.
I’m not even sure how one would type double spacing in either editor – each time you press Enter/Return, you should get a new paragraph. I’m not sure what a Ctrl-Return produces, but normally that would just appear to be a space.
The only way I can think of to easily make double spacing for a specific paragraph would be to create a custom CSS class that defines the line height you want for double spacing, and then add that class to the individual paragraph (easiest with the block editor.).
The class might be something like:
.doublespace { line-height: 200%;}
then add .doublespace in the class box on the block editor block advanced class option.