ChannelUnion v9.0

ChannelUnion takes the process of creating a string of ChannelMerge nodes to combine several mask channels off your hands. It provides you with a simple panel to select the required channels, and then creates the merge nodes under the hood. This was created to simplify generating grading masks from multiple mask layers in 3d renders, or combining different layers of roto elements.

The selection panel features a filter text box to quickly find channels. Previously selected channels will remain active for easy changes. Additionally, there's a reset button to start over, if needed, and a purely cosmetic button to autoplace the internally created nodes. 

Production-tested in Nuke 13 on Windows, but it should run in v11 and newer (any version supporting PySide2).