New posts in Optional Arguments

Connecting multiple arguments

Adjusting command behavior based on argument type

LaTeX: optional arguments with square brackets

List parsing with special input/optional arguments

\newcommand gives errors in math mode (with or without arguments)

How can one put a "[" after \item?

Optional arguments in pgfkeys?

Optional argument to an environment inside align

More than one optional argument for newcommand

How to pass an optional argument to an environment with verbatim content?