Merge

Sockets:
IN - Data/ Layer/ Filter
OUT - Data/ Filter
Description:
Combines several streams of the same kind into one. What "combine" means
depends on the mode.
Properties:
Mode
Data - merges any node with Data output into one.
Layer - merges Layers into one and converts them into Data.
Filter - merges Filters for better organisation.
Usage Notes:
- Switching the mode rebuilds the node's sockets and disconnects links of the
wrong type.
- The merge is non-destructive to each branch's own effects - collections,
layers, and pending operations from every branch all carry through. Two
branches creating the same thing are deduplicated, not doubled.