Question: how to register information for custom xkb keyboard layout using hyprland/language module

[GscheadaHamme]

I created a custom xkb keyboard layout at ~/.xkb/symbols/de_custom:

default partial modifier_keys
xkb_symbols "basic" {
    include "de(basic)"
    name[Group1] = "German, right widows key set to menu";
    key <RWIN> {[ Menu ]};
};

partial modifier_keys
xkb_symbols "nodeadkeys" {
    include "de(nodeadkeys)"
    name[Group1] = "German (no dead keys), set right widows key to menu";
    key <RWIN> {[ Menu ]};
};

Sadly, no information is shown in the waybar when I activate this layout, for each variant.
How can I provide the information needed for the module?