5. The stack: buses, folders, layers, sublayers

Items. as we described in Ship analogy, here is that stack, it has two structural item types: layers and folders. Layers hold sublayers. Folders hold layers and other folders, nested as deep as you like, but you can also add sublayers on them - like filters, blur, sharpen, curve etc.. Items are named automatically (Layer.001, Folder.002) and can be renamed (BUT you change only LABELS, if you do it trough material editor - dont touch names of nodes, they are tracked by name, if you change it, hiearchy breaks).

now each item has two buses, one is image, other is mask, you have 3 sublayer types per each, they are equivalents for each other, Color to FIll, Image to Paint, Material to Procedural

Operations on items (buttons in the main panel and the item's row):

• Add a layer, a folder, or any sublayer kind including filters.
• Duplicate deep-clones a layer or folder together with all of its images.
• Remove deletes the selection, recursively for folders.
• Reorder by dragging (currently windows only). Masks and channel wiring are rebuilt automatically.
• Copy and Paste items and sublayers through Overpaint's own clipboard.
• Mute any item or sublayer to hide it without removing anything.
• Expand and Collapse a layer's sublayer list in the panel.
• Group into Folder and Unparent to Root move things in and out of folder stacks.

Blend mode and opacity. Every sublayer has its own, using Blender's familiar Mix modes (Multiply, Overlay, Screen etc.). Erase Alpha and Add Alpha belong to the brush, see Material Paint in chapter 9.

Flatten. A folder or a layer can be flattened by hand if you do not want automatic Cascade pre-baking: its sublayers are flattened into one result and the originals are muted, not deleted. Release brings the editable stack back.