Layers: Cmd/Ctrl+Alt-click places a new layer below the current one and a new sublayer at the bottom

The reference app places a new layer below the selected layer with
Ctrl+Alt-click (Command+Option-click) on the New Layer button, and a
new sublayer at the bottom of the layer list with the same click on
the New Sublayer button. In VectorCraft that click opened Layer
Options, and New Layer and New Sublayer always added the layer above
the current layer and the sublayer on top of the layer's contents.

layer.new takes below, which adds the layer directly below the current
layer at its level, and layer.newSublayer takes bottom, which adds the
sublayer under the parent's contents. In a clipping layer the new
sublayer goes above the clipping path. Each is one undo step, and
below is refused together with top. A Cmd/Ctrl+Alt-click on the
Layers panel's New Layer and New Sublayer buttons runs them. A plain
click, an Alt-click and a Cmd/Ctrl-click work as before.

Docs: docs/mcp.md, docs/target-app-parity.md.

docs/mcp.md

@@ -2133,10 +2133,12 @@ and `layerRows`, the rows highlighted in the panel.
   inside it); a row never goes into itself or a row inside it, and a locked layer or group takes nothing. Dragging the
   selected-art square is `layer.move` with the selected objects. `node.move {id, parent?, index}` is the low-level
   form with the same nesting rules; unlike `layer.move`, it also moves a row into a locked layer or group.
-- **Buttons**: `layer.new {name?, top?, …options}` (above the current layer at its level; `top` with Ctrl/Cmd),
-  `layer.newSublayer {parent?, name?, …options}` (on top of the parent's contents), `layer.delete {ids?}` (rows with
-  what they hold; the last layer stays), `layer.locate {id?}` (highlights the selected object's row; the panel opens
-  the rows around it) and `layer.clippingMask.toggle`.
+- **Buttons**: `layer.new {name?, top?, below?, …options}` (above the current layer at its level; `top` with
+  Ctrl/Cmd; `below`, directly below the current layer at its level, with Ctrl/Cmd+Alt),
+  `layer.newSublayer {parent?, bottom?, name?, …options}` (on top of the parent's contents; `bottom`, under them but
+  above a clipping layer's clipping path, with Ctrl/Cmd+Alt), `layer.delete {ids?}` (rows with what they hold; the
+  last layer stays), `layer.locate {id?}` (highlights the selected object's row; the panel opens the rows around it)
+  and `layer.clippingMask.toggle`.
 - **Panel menu**: `layer.duplicate {ids?}`, `layer.merge {ids?}` (into the layer highlighted last, keeping the
   stacking order), `layer.flatten {id?}` (every other visible layer's art into one layer; hidden layers are deleted,
   templates stay), `layer.collectInNew {ids?}`, `layer.releaseToLayers {id?, build?}` and

docs/target-app-parity.md

@@ -709,6 +709,7 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
   The panel menu's Save Selection submenu has Save Selection…, Update Selection and Edit Selection…, enabled and run as in the Select menu, and lists the document's saved selections: choosing one selects its objects again (`select.recall`).
   `object.setProps` with `visible: false` or `locked: true` deselects every selected object that is then hidden or locked, the key object included, as the eye and lock columns do.
   Ctrl/Cmd+Alt-clicking an eye switches the other layers to Outline and the row's layer to Preview, or switches all layers back to Preview when the others are in Outline (`layer.outlineOthers`, `layer.previewAll`).
+  Ctrl/Cmd+Alt-clicking New Layer adds a layer directly below the current layer, at its level (`layer.new {below: true}`), and Ctrl/Cmd+Alt-clicking New Sublayer adds a sublayer under the contents of the layer it goes into (`layer.newSublayer {bottom: true}`), each in one undo step. The reference app's [Default keyboard shortcuts](https://web.archive.org/web/20260726060015/https://helpx.adobe.com/illustrator/using/default-keyboard-shortcuts.html) page lists these clicks for placing a layer below the selected layer and a new sublayer at the bottom of the layer list.
   Alt-clicking a layer's or sublayer's name makes it the current layer, as a click does, and selects its visible, unlocked art, as its selection square does (`layer.selectAll`, then `layer.setCurrent`); on a hidden or locked layer it clears the selection. The reference app's [Default keyboard shortcuts](https://web.archive.org/web/20260726060015/https://helpx.adobe.com/illustrator/using/default-keyboard-shortcuts.html) page lists Alt-click on the layer name for selecting all objects on the layer.
   Object › Arrange › Send to Current Layer returns the error "the target layer is locked or hidden" and leaves the selected objects where they are when the current layer is hidden or locked, or is inside a hidden or locked layer.
   Selected objects are deselected, the key object included, when a row drag moves them into a hidden layer or group, when `node.move` moves them into a hidden or locked layer or group, when Merge Selected moves them into a hidden or locked layer, when Collect in New Layer moves them into a new layer inside a hidden or locked layer, when Flatten Artwork moves them into a locked layer, and when applying a data set hides them.