i have been using the raspberry pi 400 for 6 months now and have been using dietpi for 1 month. i have been trying to find a dark theme like win10 has . im not quite sure what has happened with lxappaerance i thought i read some place there was a dark theme but i cant find it. can somebody please tell me if there is a dark theme in lxappearance please
In lxappearance / “Customize Look and Feel” you can change the window theme in “Window Border” tab. The “Nightmare” themes are pretty dark. The panel color needs to be adjusted separately in the Penal Settings > Appearance. Not sure where the color for PCManFM can be changed. So yeah sadly there is no single setting to change/apply a consistent theme for all parts of the LXDE desktop 
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oh well thanks anyway