In fact, we don't need the exact replacement. As general solution code folding infrastructure could analyze itself all
tokens LINE_COMMENT in document and extract needed codefolding tags text (like <editor-fold>/</editor-fold>)
Or ask editor kits to do something like:
doc.putProperty("folding-tokens", EnumSet.of(CppTokenId.LINE_COMMENT));
then you can use set of dedicated tokens to analyze it's content for folding tags

I'm not sure if I understand it. Since 6.5 CustomFoldManager works with lexer tokens rather then with the old Syntax
tokens. It automatically scans all tokens that belong to a primary category called "comment". I don't know off hand what
tokens and categories are produced by C++ lexer, but custom code folds should work automagically in any language that
creates its comment tokens under the "comment" primary category.

Is this the missing piece of information that you needed or did I misunderstand the problem? Thanks

I have checked your statement and  all needed is realy already in place (we have "comment" category for comment tokens
as well). Great! 

We had to add syntax based approach in the beginning of 6.5 (or even 6.1), but wasn't aware that it was added in editor
in 6.5 later on