Due to plans to port to Wayland - Development - Whonix Forum, resource constraints for running inside virtual machines, preferences of security and minimalism, choices are limited. At this time, LXQt seems the most likely next thing.
I like minimalism and less code = less possibilities for vulnerabilities. So, I did - apt remove xfce4-whiskermenu-plugin - and I use xfce panel’s built-in applications menu or app-launcher. It is absolutely enough for me. Thus I don’t need Whisker Menu at all.