This might be the smallest Obsidian plugin, but it adds the current open note to the window title, like so:

Obsidian v0.11.0 - obsidian - testing/currently-open-note-for-project-xyz.md

This is useful when you are tracking your application usage with Timing (or any other app that uses window title). Otherwise it might prove useful for context what you're doing when switching with alt-tab if your application switcher allows for filtering like contexts.app.

Through settings of this plugin it is possible to template the window title of the Obsidian app. You can specify the {{filename}}, {{filepath}}, {{vault}} or {{workspace}}. Frontmatter is also supported. For example if you have a file with the following frontmatter:

category: "Testing"

You can use the following template: Obsidian - {{frontmatter.category}}. This would result in a window title of Obsidian - Testing once you open the file. If a file doesn't have the corresponding frontmatter key, it is removed, resulting in just: Obsidian -.