For the moment x11-wm/sway doesn't have tray, but this is the smallest problem. The biggest problem is that graphics/wayland on FreeBSD it's not working, so without graphics/wayland also no x11-wm/sway on FreeBSD. The best solution is x11-wm/i3 if you are looking for a manual tilling manager, which by the way has tray support by default.
Looks like it's oly available as ports, not via pkg. However I couldn't get the sway working..
It said XDG_RUNTIME_DIR is not set...
I failed to set it up without a documentation. Anyone can point me to a FreeBSD specific documentation with sway? I am on Slim display manager
I also tried export XDG_RUNTIME_DIR=~/ but it threw bunch of red lines I can't remember now, so I forgot about it now. I still don't understand how this whole wayland thing works
Why you use slim display manager? My wayland@FreeBSD experiment worked without xorg installed at all.
register XDG_RUNTIME_DIR in your .cshrc and just type sway in console!
Good XDG_RUNTIME_DIR is /tmp/`id -u`-runtime-dir, but really it doesn't matter.