As part of the 2024 Power Platform Release Wave 1, Microsoft have moved the classic Advanced Settings menu over to the new Power Platform Environment Settings app.
The Power Platform Environment Settings app provides a modern, performant, accessible, secure, and extensible settings management experience. This app is intended to provide a single, unified experience for application developers to create settings for their applications.
However, you may have classic Themes which you may wish to edit/update/publish/export or change a logo, at this point in time (at time of writing) it’s not possible to do through the new PP Environment Settings App. Well never fear, this quick tip will help you find Classic Themes easily again.