@pkouame , about your hybrid mode patch and into next attempting to fix translucency on the "Finder top menu bar", once I noticed that replacing the "SystemAppearance.CAR" from HS in Mojave "fixed" into "solid clear color" all the sidebars windows, anyway, thanks to your experiments I understood that the "top finder menu bar" is controlled by the HIToolbox framework, however inside its Resources's subfolder there are some interesting graphics "assets" that should manage the finder top menu bar "drawing" and they are: HIToolbox.rsrc and Extras2.rsrc
The only app that can open them is "ThemePark4.1" and works only on Snow Leopard. In particular editing the Extras2.rsrc you can for example change the finder top menu bar color.
Some users in past used that app to create custom themes for OSX.
I extend this post also to "tiehfood" (not sure who is on this forum), that as you wrote from your github given a useful hint to fix the CoreUI.
edit:
Here is a very interesting discussion that explains why there is not a Extras.rsrc (for PowerPC Macs) but only a Extras2.rsc (for Intel Macs):
https://superuser.com/questions/271090/where-does-osx-leopard-store-its-gui-graphics
Also
@swamprock, editing those "resources assets" did a custom theme some years ago.
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I guess they depend from "HIToolbox" not completely fixed, that inherits, apart all the finder top menu bar, many others submenus in-apps, builded over the "Finder" engine's frameworks.