[LudiusMaximus]

Wow, this is amazing!! How do you get to know stuff like this?? :-D

Could you also think of a way to SetIgnoreParentAlpha() of alert frames that are already shown; i.e. after the resetterFunc has already been fired?

Anyway, thank you so much!


UPDATE: I think I found a way.

local collectedAlertFrames = {}
local alertFramesIgnoreParentAlpha = false
 
-- Function I call whenever I toggle UIParent's alpha. 
local function SetAlertFramesIgnoreParentAlpha(enable)
  alertFramesIgnoreParentAlpha = enable
  for _, v in pairs(collectedAlertFrames) do
    v:SetIgnoreParentAlpha(enable)
  end
end
 
local function CollectAlertFrame(_, frame)
  if not frame.IEF_collected then
    tinsert(collectedAlertFrames, frame)
    frame.IEF_collected = true
    frame:SetIgnoreParentAlpha(alertFramesIgnoreParentAlpha)
  end 
end
 
for _, subSystem in pairs(AlertFrame.alertFrameSubSystems) do
  local pool = type(subSystem) == 'table' and subSystem.alertFramePool
  if type(pool) == 'table' and type(pool.resetterFunc) == 'function' then
    hooksecurefunc(pool, "resetterFunc", CollectAlertFrame)
  end
end