[zork]

p3lim is right. /run ExtraActionBarFrame:GetParent():GetName() reveils it.

This is what I'm using atm. The frame at the darkmoonfaerie is funny. But maybe the vehicle button 1 is actionbutton 121 aswell.

This is my current implementation. Still needs testing. Not sure if the event hooking is actually required (and the show/hide may even cause trouble in combat)

--get the addon namespace
    local addon, ns = ...
    --get the config values
    local cfg = ns.cfg
    local barcfg = cfg.bars.extrabar
    if barcfg and not barcfg.disable then
     
      --holder frame
      local bar = CreateFrame("Frame","rABS_ExtraActionBar",UIParent,"SecureHandlerStateTemplate")
      bar:SetSize(barcfg.buttonsize,barcfg.buttonsize)
      bar:SetPoint(barcfg.pos.a1,barcfg.pos.af,barcfg.pos.a2,barcfg.pos.x,barcfg.pos.y)
      bar:SetHitRectInsets(-cfg.barinset, -cfg.barinset, -cfg.barinset, -cfg.barinset)
      bar:SetScale(barcfg.barscale)
      cfg.applyDragFunctionality(bar,barcfg.userplaced,barcfg.locked)
     
      --the frame
      local f = ExtraActionBarFrame
      f:SetParent(bar)
      f:ClearAllPoints()
      f:SetPoint("CENTER", 0, 0)
      f.ignoreFramePositionManager = true
     
      --the button
      local b = ExtraActionButton1
      b:SetSize(barcfg.buttonsize,barcfg.buttonsize)
      bar.button = b
     
      --style texture
      local s = b.style
      s:SetTexture(nil)
      local disableTexture = function(style, texture)
        if not texture then return end
        if string.sub(texture,1,9) == "Interface" then
          style:SetTexture(nil) --bzzzzzzzz
        end
      end
      hooksecurefunc(s, "SetTexture", disableTexture)
     
      --register the event, make sure the damn button shows up
      bar:RegisterEvent("UPDATE_EXTRA_ACTIONBAR")
      bar:RegisterEvent("PLAYER_REGEN_ENABLED")
      bar:SetScript("OnEvent", function(self, event, ...)
        if (HasExtraActionBar()) then
          self:Show()
          self.button:Show()
        else
          self:Hide()
        end
      end)
     
    end --disable