Now that ExpressionManager appears to be working, we need a GUI to help people create and debug the more complex expressions it enables.
The attached .jpg files are screen captures of how ExpressionManager renders errors. If it tries to parse an invalid Expression (or other macro, INSERTANS, etc.), it:
(1) Highlights the entire expression yellow
(2) Red-Boxes characters that are known syntax errors -like undefined variables or functions, or unsupported syntax
(3) Provides ToolTips for both - so a mouse-over will provide an error message.
If people want to play with the ExpressionManager directly, there is a patch here. Via that patch, it is tightly integrated with LS1. It is working for me, but needs to be tested and validated by others before we can seriously consider incorporating it into the main branch.