Another way would be to hook directly into
SCENE_MANAGER
Lua Code:
local yourFragment = ZO_SimpleSceneFragment( yourControl )
-- this scene controls the hud when the recticle is active
local hudScene = SCENE_MANAGER:GetScene( "hud" )
hudScene:AddFragment( yourFragment )
-- this scene controls the hud when the mouse is active ( after you hit the '.' key )
local hudUIScene = Scene_MANAGER:GetScene( "hudui" )
hudUIScene:AddFragment( yourFragment )
in a similiar way you can 'append' your controls to the Inventory, etc.
the downside is there is no easy way to 'remove' it since there is no
RemoveFragment function
but it shut be possible to remove the fragment from the scene and the force an update of the scene e.g. toggle the scene twice.