Currently the only way to add suppressions is via absolute file paths.
This does not work well for complex maven projects, where you are interested to inherit suppression from the parent (which is not part of the reactor).

It would be nice if suppressions could be either provided in an inline fashion (i.e. within the pom.xml) or could be also loaded from a dependency file (in zip/jar format)

There is very similar feature already available in the formatter-maven-plugin which should give some hints on how to implement this: https://code.revelc.net/formatter-maven-plugin/examples.html#Basic_Configuration_Using_External_Resource