SparqlBlocks is a library to build SPARQL queries visually with blocks, based on the Blockly framework. It might be a good basis for explaining Wikidata SPARQL queries for non-programmers, but it needs some work:

• it is not very obvious how to create a query; there should be a tutorial or in-app help text
• there is no nice way to create property or item blocks; you need to find the right block type in the sidebar and fill in the Q/P number. There should be some kind of label-based autocomplete.
• more generally the sidebar should be rearranged to emphasize basic functionality and hide more complex functionality
• there seems to be no way to use the label service; Q/P ids should come with labels