As a user I want single expression language that I can use in instead of long list of expression evaluators for both evaluation and enrichment
Nested expressions should be working in every place.
ExpressionManager must be consistent. isValidExpressions must return true for any valid expression including nested expressions.
We need a wiki page to create/show example of how this should work, can't you add an example of how you understanding nested expressions there, once one of use creates a page?