Hmmm, it works perfectly now. Although it is not Bolstering this week in mythic +.
If someone interested about this and want to have a go, you can just change the customfilter as below to test it.
Code:
local function customFilterForBolster(element, _, button, name, _, _, _, _, _, _, _, _, _, spellID)
if name then
element.bolster = element.bolster + 1
if not element.bolsterIndex then
element.bolsterIndex = button
return true
end
end
end
And there would be just one icon shows up and it counts how many auras the unit owns.