In V11.5 and later, it is possible to escape the field names by wrapping them in square brackets, thus identifying them directly as fields so they do not conflict with function names.
This is useful if you have a field name that is the same as a function name. For example, if you have a field named "year" and you want to set a filter on year being 2000, so the filter string would be "year = 2000". The parser would fail because it identified "year" as a function with the wrong syntax.
The new syntax would be "[year] = 2000", which the parser unambiguously interprets as a field named "year".
The parser allows the content of "" to be composed by any character excluding "]", space, tabs, newline, and linefeed.