TailorKey

OneShot Shift (&sticky_key_modtap LSFT LSFT)

This is a common ergonomic feature used in the ZMK keyboard community that helps you use Shift without holding it down.

It combines two ways of using Shift into one key.

Tap the key: activates one-shot Shift and turns on Shift for just the next key you press
Hold the key: works like a normal Shift key (you hold it while typing)

How-to:

Copy the DTS ZMK code below into the Custom Behavior Field in the MoErgo Layout Editor, then create a Custom Behavior key binding as shown below.

Custom value: &sticky_key_modtap LSFT LSFT

// Copy this ZMK DTS into the Custom Defined Behaviors field

behaviors {

sticky_key_modtap: sticky_key_modtap {

compatible = "zmk,behavior-hold-tap";

flavor = "tap-preferred";

tapping-term-ms = <250>;

#binding-cells = <2>;

bindings = <&kp>, <&sticky_key_oneshot>;

};

sticky_key_oneshot: sticky_key_oneshot_macro {

compatible = "zmk,behavior-macro-one-param";

wait-ms = <0>;

tap-ms = <0>;

#binding-cells = <1>;

bindings

= <&macro_param_1to1>

, <&macro_tap &sticky_key_quickrel MACRO_PLACEHOLDER>

;

};

sticky_key_quickrel: sticky_key_quick_release {

compatible = "zmk,behavior-sticky-key";

#binding-cells = <1>;

bindings = <&kp>;

release-after-ms = <500>;

quick-release;

ignore-modifiers;

};

}; // <--- if THIS semicolon is the missing your build to fail

Layout Editor macro UI does not allow me to add a parameter to a Custom Behavior.

When I make the change in the json and import, it works fine.

⚠️jul 2026 Don't use below - it will break in the next version of Layout Editor and this will all be native available in the GUI.

LLM: Why do we need the Macro?

The short answer: It fixes a tricky timing bug in ZMK.

Without the macro, combining a Hold-Tap directly with a Sticky Key causes them to fight over when the key is technically "released." Here is what happens behind the scenes:

The Problem (Without the Macro): If you assign the Sticky Key directly to the tap action, ZMK ties the sticky behavior to your physical finger. If you tap the key but lift your finger a tiny fraction of a second too slowly, ZMK gets confused. It thinks you "held" and then "released" the sticky key, which immediately cancels the Shift before you can type your next letter.

The Solution (What the Macro Does): The macro acts as a lightning-fast middleman. When you tap the physical key, the macro steps in and says, "I'll take it from here." Because the macro is set to waitMs: 0 and tapMs: 0, it triggers a perfectly clean, instant, digital "press and release" of the sticky key in zero milliseconds.

This completely separates the sticky Shift from your physical finger's timing. It guarantees the one-shot Shift activates flawlessly every single time, no matter how clumsily you press or release the physical switch.

The Parameter Messenger: Additionally, because ZMK needs to know which key to make sticky (in this case, LSHFT), the macro uses that &macro_param_1to1 line. It simply grabs the LSHFT parameter you assigned to the Hold-Tap and safely passes it down into the Sticky Key.

Page updated

Google Sites

Report abuse