[Zax]

Interesting, SDPhantom. Thank you.

I have to say that I'm not sure how to adapt my code based on what you found.
As a reminder, I use the following basic code for a button with a macrotext attribute. It works fine on WoW 9.x:

local frame = CreateFrame("Frame", "Test", UIParent, "SecureHandlerStateTemplate")
    frame:SetSize(40, 40)
    frame:SetPoint("TOPLEFT", UIParent, 10, -150)
 
    local button = CreateFrame("Button", "TestBtn", frame, "SecureActionButtonTemplate")
    button:ClearAllPoints()
    button:SetSize(32, 32)
    button:SetPoint("CENTER", frame)
    local texture = button:CreateTexture("$parent_tex", "BACKGROUND")
    texture:SetAllPoints(true)
    texture:SetTexture(GetSpellTexture(783)) -- "Travel Form"
    button.texture = texture
 
    button:RegisterForClicks("LeftButtonUp", "RightButtonUp")
    button:SetMouseClickEnabled(true)
    button:SetAttribute("type", "macro")
    button:SetAttribute("macrotext", "/abs")
    
    ------ testing purpose
    button:SetScript("PostClick", function(self, arg1)
        print("POSTCLICK: Clicked button=", self:GetName(), "  macroTxt=", self:GetAttribute("macrotext"))
    end)
end

Also, I believe the code you found concerns the raid markers (placed on units) and not the ground markers (placed on... the ground ).