[Feature Request]: Comfy UI custom UI layout and elements.

### Is there an existing issue for this?

- [X] I have searched the existing issues and checked the recent builds/commits

### What would your feature do ?

Might be an idea that would break any coder that tries to do it... But wit would be amazing to have "UI Customization" functionality. I can see the "Theme" button on the left. Which I would never use so I would love functionality where I can customize the UI elements. It means I can get rid of that "theme" button and replace it with a "clear canvas" button or some other UI element or command or something. My hand isn't always at the keyboard to use keyboard shortcuts. And also could open up the possibilities of people making really cool "Custom UI" layouts for doing different kinds of work in comfy. Think of maybe an "Inpainting/Outpainting" ComfyUI layout. Or a "Menuless" layout where you just have little buttons in the menu ribbons that you could use instead of going into menus.

Users could even provide a 32px square image to use as the button icon themselves or something?

I mean it is called ComfyUI... How awesome would it be to customize the UI?

### Proposed workflow

A "Layout Manager" module where you could have a manager that could add button elements to the different menu areas. Provide PNG image for the graphic the button would have in the UI. Ability to remove UI elements you don't want (Like the theme button) since I always use dark mode.

### Additional information

_No response_

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-1654-Feature-Request-Comfy-UI-custom-UI-layout-and-elements-15f6d73d36508167b0f0e7fedbd7588c) by [Unito](https://www.unito.io)