The Meqbrowser as you might expect from the name offers you the capability to browse your Measurement Equation tree.

In the 'Trees' part of the window on the left, expand the 'Root nodes', then the 'VisDataMux'.

You'll see a bunch of nodes called 'sinks'. Sinks put visibilities into your MS, and there will typically be a sink per baseline, e.g. sink:3:5 deals with the baseline formed between antennas 3 and 5.

(The nodes that read visibilities from a MS are called spigots. Since this is a regular 'sim only' simulation there aren't any of these.)

It's a good idea to try to relate what's going on in your simulation or calibration to what you see in the tree. Remember the 'onion skin' matrices in the Measurement Equation? You can hopefully see how MeqTrees implements this with the source coherency matrices at the heart of it all. The annotated diagram below might help.