diff --git a/config/base.keymap b/config/base.keymap
index a22efc2..67c9902 100644
--- a/config/base.keymap
+++ b/config/base.keymap
@@ -46,6 +46,10 @@
     quick-tap-ms = <QUICK_TAP_MS>;
 };
 
+&leader {  // leader-key config
+    timeout-ms = <220>;
+};
+
 /* Homerow mods */
 
 #define KEYS_L LT0 LT1 LT2 LT3 LT4 LM0 LM1 LM2 LM3 LM4 LB0 LB1 LB2 LB3 LB4  // left hand
@@ -207,6 +211,9 @@ ZMK_MACRO(win_sleep,
     bindings = <&kp LG(X) &kp U &kp S>;
 )
 
+// Sticky shift + leader
+ZMK_MACRO(shift_leader, bindings = <&sk LSHFT &leader>;)
+
 // misc aliases
 #define CANCEL      &kp K_CANCEL             // cancel caps-word, num-word and smart-mouse
 #define DSK_PREV    &hmr LCTRL LG(LC(LEFT))   // previous desktop
diff --git a/config/leader.dtsi b/config/leader.dtsi
new file mode 100644
index 0000000..e9c01c9
--- /dev/null
+++ b/config/leader.dtsi
@@ -0,0 +1,47 @@
+/*                KEY POSITIONS
+
+  ╭─────────────────────╮ ╭─────────────────────╮
+  │ LT4 LT3 LT2 LT1 LT0 │ │ RT0 RT1 RT2 RT3 RT4 │
+  │ LM4 LM3 LM2 LM1 LM0 │ │ RM0 RM1 RM2 RM3 RM4 │
+  │ LB4 LB3 LB2 LB1 LB0 │ │ RB0 RB1 RB2 RB3 RB4 │
+  ╰───────╮ LH2 LH1 LH0 │ │ RH0 RH1 RH2 ╭───────╯
+          ╰─────────────╯ ╰─────────────╯
+
+Note: The leader sequence must be pressed exactly as defined to be triggered.
+To capitalize a letter, hold the shift key (or tap sticky-shift) *before*
+tapping the leader key. */
+
+/* German umlauts */
+
+ZMK_LEADER_SEQUENCE(de_ae,      &de_ae,         LM4 RM2)  // ä
+ZMK_LEADER_SEQUENCE(de_oe,      &de_oe,         RM4 RM2)  // ö
+ZMK_LEADER_SEQUENCE(de_ue,      &de_ue,         RT2 RM2)  // ü
+ZMK_LEADER_SEQUENCE(de_eszett,  &de_eszett,     LM2 LM2)  // ß
+
+/* Greek letters */
+
+ZMK_LEADER_SEQUENCE(el_alpha,   &el_alpha,      LM4)      // α
+ZMK_LEADER_SEQUENCE(el_beta,    &el_beta,       LT0)      // β
+ZMK_LEADER_SEQUENCE(el_gamma,   &el_gamma,      LM0)      // γ
+ZMK_LEADER_SEQUENCE(el_delta,   &el_delta,      LB1)      // δ
+ZMK_LEADER_SEQUENCE(el_epsilon, &el_epsilon,    RM2)      // ε
+ZMK_LEADER_SEQUENCE(el_zeta,    &el_zeta,       LB4)      // ζ
+ZMK_LEADER_SEQUENCE(el_eta,     &el_eta,        RB1)      // η
+ZMK_LEADER_SEQUENCE(el_theta,   &el_theta,      LB0)      // θ
+ZMK_LEADER_SEQUENCE(el_iota,    &el_iota,       RM3)      // ι
+ZMK_LEADER_SEQUENCE(el_kappa,   &el_kappa,      RB0)      // κ
+ZMK_LEADER_SEQUENCE(el_lambda,  &el_lambda,     RT1)      // λ
+ZMK_LEADER_SEQUENCE(el_mu,      &el_mu,         RM0)      // μ
+ZMK_LEADER_SEQUENCE(el_nu,      &el_nu,         RM1)      // ν
+ZMK_LEADER_SEQUENCE(el_xi,      &el_xi,         LB3)      // ξ
+ZMK_LEADER_SEQUENCE(el_omikron, &el_omikron,    RM4)      // ο
+ZMK_LEADER_SEQUENCE(el_pi,      &el_pi,         LT1)      // π
+ZMK_LEADER_SEQUENCE(el_rho,     &el_rho,        LM3)      // ρ
+ZMK_LEADER_SEQUENCE(el_sigma,   &el_sigma,      LM2)      // σ
+ZMK_LEADER_SEQUENCE(el_tau,     &el_tau,        LM1)      // τ
+ZMK_LEADER_SEQUENCE(el_upsilon, &el_upsilon,    RT2)      // υ
+ZMK_LEADER_SEQUENCE(el_phi,     &el_phi,        LT2)      // ϕ
+ZMK_LEADER_SEQUENCE(el_chi,     &el_chi,        LB2)      // χ
+ZMK_LEADER_SEQUENCE(el_psi,     &el_psi,        RT3)      // ψ
+ZMK_LEADER_SEQUENCE(el_omega,   &el_omega,      LT3)      // ω
+