A macro operator is a planning operator that is generated from a sequence of actions. Macros have mostly been used for macro planning, where the planner considers the macro as a single action and expands it into the original sequence during execution, but they can also be applied to other problems, such as maintaining a plan library. There are several approaches to macro operator generation, which differ in restrictions on the original actions and in the way they represent macros. However, all existing approaches are either restricted to STRIPS domains, only work on grounded actions, or they do not synthesize macros but consider the original sequence instead. We study the synthesis of macro operators for ADL domains. We describe how to compute the parameterized preconditions and effects of a macro operator such that they are equivalent to the preconditions and effects of the respective action sequence and prove the correctness of the synthesized macro operators based on a Situation Calculus semantics for ADL. We use the synthesis method for ADL macro planning and evaluate it on a number of domains from the IPC. As a second application, we describe how macro operator synthesis can be useful for maintaining a plan library by computing the precondition and effects of the parameterized library plans.