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Combining workflows is easy.
Since they have the same source, you could copy all the tools after the source (assuming all the other tools are different) in one workflow into the other. Then just connect the source to the new tools.
Input tools really have many outflow anchors even though you only see one.
As for SPC, I'm not familiar with it. But if you provide a little bit of background into what you want to do then we can probably help.