The band source cant be selected for the rayleigh correct tool in graph builder

I need to process a MERIS dataset via tool graph. But the sources bands in Rayleigh correction tool cannot be used in Graph Builder. The latest version SNAP has been installed on my windows7 OS.

That’s an issue with the GraphBuilder. Some operators don’t work well.
We have it on the development agenda:"graph%20builder" But this might not be solved with the next release.
Workarounds have been discussed here:
SNAP 6.0 can't read bands by rayleigh correction in graph builder
and here:
Batch processing/graph file problem