the function Macro.update_meta/2 is documented as useful to manipulate AST metadata:
Applies the given function to the node metadata if it contains one.
This is often useful when used with
Macro.prewalk/2to remove information like lines and hygienic counters from the expression for either storage or comparison.
This means that AST metadata can be accessed for reads and writes, but I cannot find a document explaining the format and semantics of all possible AST metadata entries.
Do you know the link for the document explaining AST metadata?