Yes - this is at the top of things for me to fix.So here's something I'm pretty sure I used to be able to do but can no longer do.
Load an object (I'm using V4 but it doesn't matter). Bring up Octanes material list. Copy an RGBSpectrum node. Change that node to a Mix node. You can't paste the RGBSpectrum node into texture1 or texture2 unless you change the node type to something else first.
This is an example but it appears you can't paste any node into a node listed as [Not Connected] even if you could change that node to the type you are trying to paste. There's a work around of course, just seems awkward and I'm not sure if it's intentional.
Paul