If it is to insert in content, Xtreme has a Widget area shortcode that you may be able to use.
Crete a new widget area using the per page widget area box in “Sidebar and layout”, then place the flex widget in it, then insert that widget area with the shortcode.
Alternatively, the Block editor allows you insert a widget block, that said, I am not seeing the weaver widgets in the list of widget block.
@weaver, would it be possible for all Weaver Widgets (extra menu, flex columns etc….) to be available in the list of widget blocks?