An existing addon ? Probably one of the action bar addons maybe has something. Otherwise ...
Looking at the blizzard code it looks like the MainMenuBar is also doing something to put things back.
https://www.townlong-yak.com/framexm...ainMenuBar.lua
https://www.townlong-yak.com/framexm...ingManager.lua
StatusTrackingManagerMixin:UpdateBarsShown is executed after any statusbar event is triggered
StatusTrackingManagerMixin:LayoutBars(visBars) is called at the end of that function
which calls self:GetParent():OnStatusBarsUpdated() which is MainMenuBarMixin:OnStatusBarsUpdated()
which then calls MainMenuBarMixin:SetPositionForStatusBars()
LayoutBars essentially repositions the bars in line with their parents position which by default is the MainMenuBar. So outside of re-parenting and dealing with any issues arising outside of that you might be able to hook into StatusTrackingManagerMixin:LayoutBar(bar, barWidth, isTopBar, isDouble) and reset the layout of each bar as you wish it to be.
I haven't played with mixin overriding to know if it is possible though.