I forgot to include a BeginBlock in the example above. Editing the post loses my font settings and will not allow me to set the font on any text, so consider this as the BeginBlock in the post above.
Thanks for your response. Yes, you understood my query correctly. I want to end the "bracketed text" lexem on either the character "]" OR the last character before a quotation mark. The reason for this is that bracketed text does not support sublexems, but quoted text does support them. Bracketed text can be inside quotation marks, and it should highlight correctly, but quoted text cannot be inside brackets. Without the requested support for lookaround assertions, we run into the problem that a "[" character inside of quotation marks will open a bracketed text lexem, which never gets closed because sublexems are not supported.
Here is an example of the problem:
I am currently ending the bracketed text lexem on "]" OR quotation marks, but then the quotation mark lexem remains open. Being able to do lookahead/behind would prevent this problem from occurring. Ending the bracketed text lexem on a quotation mark is "more" acceptable than not doing this, because quoted text allows all sublexems, but it is still not ideal, as it does not display correctly and it creates problems when processing the ConfigStack.
Thank you for your consideration of this issue, and I will be very pleased if there is any workaround to accomplish my goal.