In case anyone else absolutely needs vec4 attributes, here's a workaround I came up with. Just create a vec4 property node and name it "TEMP_UV3_CHANNEL", and treat it like a UV3 node. Also make sure to put a UV node in your canvas somewhere set to input 2 (don't connect it to anything).
Then once you've built your shader compile it and select the compiled asset in Unity and run "Tools/ShaderForge/Replace UV3 Channel". This will crap out a new shader next to the original with correct UV3 attributes.
In case anyone else absolutely needs vec4 attributes, here's a workaround I came up with. Just create a vec4 property node and name it "TEMP_UV3_CHANNEL", and treat it like a UV3 node. Also make sure to put a UV node in your canvas somewhere set to input 2 (don't connect it to anything).
Then once you've built your shader compile it and select the compiled asset in Unity and run "Tools/ShaderForge/Replace UV3 Channel". This will crap out a new shader next to the original with correct UV3 attributes.
https://gist.github.com/karl-/e13ff3a6e74a3a69ba49