IDE 2.0.3 Undocking Serial Monitor (?)

For reference, here is the issue the Arduino IDE developers are using to track the need for Serial Monitor to be a separate window:

If you have a GitHub account, you can subscribe to that issue to get notifications of any new developments related to this subject.

Work is in progress now to add the missing baud rates:

Are you aware that Arduino IDE 2.x comes with multiple pre-installed themes you can pick from?

Arduino IDE 1.x didn't have a GUI for customizing the theme either. In fact, I can't think of a single application that does. Even Windows hasn't provided such a feature for quite some years now.

Perhaps you would like to contribute the code changes required to add the feature you miss to this free open source software project?

As for customizing the Arduino IDE theme, you might be interested in this information a forum member shared, which does include an option for GUI-based theme customization:

Note that support for custom themes was lost in the Arduino IDE 2.0.3 release, but it has already been fixed in the nightly build.