If you just want to tweak specific parts of your portable setup:
Each theme is a single CSS file plus an assets folder. I added a tiny script (batch on Windows, shell for Linux) that copies the active CSS into Emby's custom.css path before launching the server. That let me carry multiple themes and switch instantly without changing the server settings each time. emby css themes portable
: A high-contrast theme featuring true black (#000000) backgrounds and blue accents, optimized for power efficiency on OLED screens. Plex-Inspired If you just want to tweak specific parts