The macro transient-define-prefix is used to define a transient.
This defines the actual transient prefix command (see Defining Transients) and adds the transient’s infix and suffix bindings, as
described below.
Users and third-party packages can add additional bindings using
functions such as transient-insert-suffix (see Modifying Existing Transients). These functions take a “suffix
specification” as one of their arguments, which has the same form as
the specifications used in transient-define-prefix.