Napit

Set right Alt as compose. Add to shell init or .xsessionrc:

setxkbmap -option compose:ralt

Or use the menu key if ralt is bound elsewhere:

setxkbmap -option compose:menu

<Multi_key> <a> <e> : "ä"
<Multi_key> <o> <e> : "ö"
<Multi_key> <a> <o> : "å"

ae → ä, oe → ö, ao → å. Log out and back in. GTK apps pick this up immediately.

setxkbmap fi        # Finnish layout
setxkbmap us        # restore

Finnish layout: ä on ; key, ö on ' key, å on ] key (ANSI). Bind both commands to a WM keybind for fast toggle.

Free, open source. Installs compose key behavior identical to Linux.

github.com/samhocevar/wincompose — runs in system tray. Default compose key: right Alt.

; place in shell:startup folder
:*:ae::ä
:*:oe::ö
:*:ao::å
:*:AE::Ä
:*:OE::Ö

Settings → Time & Language → Language & region → Add Finnish. Toggle with Win Space.

Settings → General Management → Language and Input → On-screen keyboard → Samsung Keyboard → Text shortcuts → Add shortcut.

Set: ae → ä, oe → ö, ao → å.

Settings → General Management → Language and Input → On-screen keyboard → Samsung Keyboard → Languages and types → Manage input languages → add Finnish.

Globe icon on keyboard toggles between English and Finnish. ä and ö appear as primary keys.

Long-press a → popup shows diacritics including ä. Long-press o → ö. Slide to select.

Gboard settings → Languages → Add keyboard → Finnish. Globe key switches layout. ä and ö become primary keys.

Gboard settings → Dictionary → Personal dictionary → select language → add entry. Shortcut: ae, Word: ä.

Same as Samsung: long-press a or o, slide to diacritic.

Amazon keyboard: long-press a → diacritic picker includes ä. Long-press o → ö.

Or add Finnish: Settings → Keyboard & Language → Current Keyboard → add Finnish. Toggle from spacebar.

The Amazon folio keyboard has no dedicated ä/ö keys. Options in order of reliability:

Set unicode mode to match host OS. In config.h:

#define UNICODE_SELECTED_MODES UC_LNX, UC_WINC, UC_MAC

Cycle with UC_NEXT. Define characters in keymap.c:

enum unicode_names { AE_LOWER, AE_UPPER, OE_LOWER, OE_UPPER, AA_LOWER };

const uint32_t PROGMEM unicode_map[] = {
  [AE_LOWER] = 0x00E4,   // ä
  [AE_UPPER] = 0x00C4,   // Ä
  [OE_LOWER] = 0x00F6,   // ö
  [OE_UPPER] = 0x00D6,   // Ö
  [AA_LOWER] = 0x00E5,   // å
};

Map to layer keys as UP(AE_LOWER, AE_UPPER) for case-sensitive pairs.

If board supports Via/Vial: open GUI, create a layer, assign UC(0x00E4) for ä, UC(0x00F6) for ö. No compile step.

&key_ae {
  compatible = "zmk,behavior-macro";
  #binding-cells = <0>;
  bindings = <&macro_tap &kp LC(LS(U))>,
             <&macro_type_unicode 0x00E4>;
};

Nordic layer accessed via held key, not toggled. Logical placements:

On 40% boards: tap-dance on a low-frequency key (capslock, enter, or right-side mod) — tap for original, hold for Nordic layer.

Bind UC_NEXT to a reachable key (e.g. Layer + Esc). QMK remembers the mode in EEPROM. One keypress when switching machines. Everything else stays the same.