Thanks for this package, it is a great idea.
hologo implements a very good mechanism for composing *TeX logos. Is that possible to interact with it and to adapt the different logos using both hologo and metalogox?

In metalogox.sty please replace

\RequirePackage{xparse}

with

\@ifl@t@r\fmtversion{2020-10-01}{}{\RequirePackage{xparse}}

because

"This package is deprecated in favor of methods integrated into the LaTeX kernel from 2020-10-01"
(https://www.ctan.org/pkg/xparse).

metalogox v1.02—2024/01/12

bookmarks:
...

• Change History and Index
• ChangeHistory
• Index
  • A
  • B
    ...

I think that

• either there should be no combined entry "Change History and Index" but only "Change History" and "Index"
• or "Change History" and "Index" should be subentries to "Change History and Index", not entries at the same level.

... looks like it could be adjusted some.

The default logos with Arsenal font (https://ctan.org/pkg/arsenal) look rather cramped. Using \usepackage{metalogox}\adjustlogos{alegreya} makes them better. Adding autodetection of Arsenal and settings close to Alegreya ones will be a good idea.

In metalogox.sty maybe add a % after Did not find font \MLX@@thisfont.\MessageBreak.