iris shift+backspace = delete

keymap.c

bool process_record_user(uint16_t keycode, keyrecord_t *record) {
    static uint8_t saved_mods   = 0;
    uint16_t       temp_keycode = keycode;

    // Filter out the actual keycode from MT and LT keys.
    if ((keycode >= QK_MOD_TAP && keycode <= QK_MOD_TAP_MAX) || (keycode >= QK_LAYER_TAP && keycode <= QK_LAYER_TAP_MAX)) {
        temp_keycode &= 0xFF;
    }

    /* uprintf("KL: kc: %u, tk: %u, col: %u\n", keycode, temp_keycode, record->event.key.col); */

    switch (temp_keycode) {
        /* case BSP_DEL: */
        case KC_BSPACE:
            if (record->event.pressed) {
                saved_mods = get_mods() & MOD_MASK_SHIFT;

                if (saved_mods == MOD_MASK_SHIFT) {  // Both shifts pressed
                    register_code(KC_DEL);
                } else if (saved_mods) {   // One shift pressed
                    del_mods(saved_mods);  // Remove any Shifts present
                    register_code(KC_DEL);
                    add_mods(saved_mods);  // Add shifts again
                } else {
                    register_code(KC_BSPC);
                }
            } else {
                unregister_code(KC_DEL);
                unregister_code(KC_BSPC);
            }
            return false;
    }
    return true;
}