The EnableParseRule command turns on the specified parse rule(s) in the Typesetting package for use in 2-D input, while the DisableParseRule command turns off the specified parse rule(s) in the Typesetting package for use in 2-D input.

There are too many rules to be able to list them all here, but all are available in the Rules area of the interactive Typesetting Assistant.

As a simple example, the rule  corresponds to the capability of parsing the function  with a symbolic subscript (say ) as a function a single variable (say ) as the BesselJ function ().