If you have not done so already check out the Themes in Settings > Appearance > Themes > Manage, some already do parts.
1. Bad UX in my eyes as some parts are static and some are based on the currently selected pane, and AFAIK not possible
2. The current position is close to where you would expect these to be in a browser and pretty much every other software, this would be bad UX I feel like, and AFAIK not possible.
6. This would be problematic once there a many plugins in that sidebar, or a plugin provides many options(just take a look at how many options the Graph Analysis plugin provides)
7. There are multiple solutions to this:
- This snippet for folders
- The Icon Folder community plugin.
- The Supercharged Links community plugins for note icons based on frontmatter text
- you can right click a folder to create the note in, or go to
Settings > Files & Links > Folder to create new notes in for configuration
- The Style Settings community plugin allows for authors of themes to expose these settings.