Sure, it's the best time while the new version is in development ๐
Viewing post in RPG Maker MZ Plugin: QuestLog comments
You can already change the window skin in the current version with the plugin parameters, no JavaScript needed, just a window skin file to place in the /system folder
Also you can change the RGB tone (from 0 (min) to 255 (max)) always from plugin parameters
I can think about adding the opacity option in v2.0 ๐