Welcome to the board!
Not to bore (or frighten) you with deep dives, but the filters that inhabit the
gmic-qt plug-in are largely implemented through (some quite large) pipelines of G’MIC commands; conceptually, they operate at a larger scale than the ‘building blocks’ constituting the G’MIC Technical Reference (and which go into the building of pipelines that
gmic-qt filters contain). Post 15: Shedding light on all Inpaint (patch-based) parameters? does not address any aspect of Align Layers but does explore some of the aspects of how parameter settings of
gmic-qt filters find their way into the underlying G’MIC pipelines, which operate at the heart of the filters. Those of us with some expertise in G’MIC scripting can spend a non-trivial amount of time tracing parameters to scripts to grasp how parameter settings give rise to image processing behaviors. It is not insurmountably hard, but it takes time. In an Ideal World, each filter would have a page or two of documentation, but many (most?) filter writers are far more talented at G’MIC scripting than dealing with the English language, a challenge even to native speakers such as myself. So filter documentation lags. In the absence of documentation, those of us who can, and who feel the itch to know intensely enough, dive into the script, as noted in the IPaint article. This is not a greatly satisfying answer, alas, but it is the best I can give.
How to create a custom filter in the G’mic plug in may be a bit dated, but broadly goes into how gmic-qt filters are built. The text dates back to the day when this was largely a Gimp-oriented task, but the basic principles have changed little.