Please add "paint layer opacity" and a paint bucket fill tool for the paint layer in Mask Editor

### Feature Idea

Reason: For color masks. I use the mask editor to create color masks with the paint layer creating multiple masks in one image that are later separated by color in a different node. The paint bucket tool would allow me the create a black canvas over the image quickly instead of using the brush. The paint layer opacity would allow me to see through the paint like you would with the mask layer, right now I have to turn off the paint layer visibility completely to see where I'm painting.

instead of a paint layer paint bucket tool another option would be to add a "hide image in output" option. So you'd only get the paint layer in the image output with a black background.

### Existing Solutions

_No response_

### Other

_No response_

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*This issue is transferred from: https://github.com/comfyanonymous/ComfyUI/issues/9925*

Original issue was created by @DoozyO at 2025-09-18T14:57:27.000Z

**Original Comments:**

- @christian-byrne:

Could you make the request in https://github.com/Comfy-Org/ComfyUI_frontend? You can just copy and paste there. Thank you

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-6405-Please-add-paint-layer-opacity-and-a-paint-bucket-fill-tool-for-the-paint-layer-in-M-29c6d73d36508161a79cc4c8759927f2) by [Unito](https://www.unito.io)

No file, test, or entry point is named. Start by locating the Mask Editor's paint-layer controls and the existing mask-layer opacity behavior; clarify whether both opacity and bucket fill are required or whether the black-background alternative is preferred. Define completion criteria and tests for the selected interaction.

Written by the indexing model from the issue text.