You will find plenty of FOSS stuff for these and I dont think it would be too hard to integrate. If there are symbols missing drop me a line or create a pull-request. To put a math symbol next to the lines which connect boxes I havent modified your foreaching but just added some nodes with the appropriate positioning.
Detexify is an attempt to simplify this search.
Online WYSIWYG Mathematics Editor Equation Editor fast and powerful Editing features inputting Normal text Math symbols and drawing GraphDiagram in one single editor help writing Math Document much easier. Symbols can also be trained here. There are no approved revisions of this page. Example AsciiMath between for example.