Shoes 3.3.4 will probably have a systray pseudo widget. Beta for Windows for feedback. You can read the manual which has this test program

Shoes.app do
stack do
para "Press button and look in your systems notification area"
ctr = 0;
button "Notify" do
ctr += 1
icp = ''
if ctr % 3 != 0
icp = "#{DIR}/static/shoes-icon.png"
else
icp = "#{DIR}/static/shoes-icon-red.png"
end
systray title: "Notify Test", message: "message ##{ctr}", icon: icp
end
end
end

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