PL-language specific: l goes before ł, Klik goes before Kłik, which is correct. Why then Płak and Płik go before Plik ???

[SebastianMC]

To be investigated. View in Obsidian for both, standard Obsidian UI sorting and the a-z custom sorting:

to make it more confusing, view at file system level (macOS finder), sorting by name:

[SebastianMC]

The reason for strange behavior clarified: the sorting rules for national characters are driven by OS language settings (global or per application - for Obsidian in this case).

My default system locale is English, and with that settings, the PL national characters aren't treated correctly in sorting (in finder, in Obsidian, in any other app which takes into account the locale).

This is also confirmed in this comment on Obsidian forum.

After changing the language to Polish (specifically for Obsidian app on macOS) the sorting started to behave correctly, both for standard Obsidian UI sorting and for custom sort a-z orders:

It is a topic worth mentioning in the documentation of the plugin