Possibility to customize how the navigation tree is processed

I have a project where the navigation tree looks like this:

* xref:index.adoc[]
* xref:page1.adoc[]
* xref:page2.adoc[]
* xref:page3.adoc[]
* Group Y
** xref:page4.adoc[]
** xref:page5.adoc[]
** xref:page6.adoc[]

If I run Antora Assembler, it will consider that

• index, page1, page2, page3 are level 1 sections
• Group Y is also a level 1 section
• page4, page5, page6 are level 2 sections

While I fully understand the logic, in my case it would make much more sense, at the PDF level, to completely ignore Group Y, and to have all pageX elements considered as level 1 sections. My choice lies in the fact that I don't find it easy in Asciidoctor PDF to define clear "top level parts" that could eg. nicely separate different chapters with page breaks, therefore I would be better with ignoring such groupings of sections.

Is it planned to be able to customize how Antora Assembler processes the navigation tree, to allow such cases?

(By the way, thanks a lot for the current Antora Assembler, it already works extremely well!)