foundry/Data/modules/z-scatter/module/control.js

import { getSetting, setSetting } from './settings.js';
function addControl(sceneControls) {
    if (!game.user.isGM)
        return;
    const tokenControl = sceneControls.find((c) => c.name === 'token');
    tokenControl.tools.push({
        name: 'size-snap',
        title: 'Size Snap',
        icon: 'fas fa-diagram-venn',
        toggle: true,
        active: getSetting('snapTokens'),
        onClick: (toggled) => setSetting('snapTokens', toggled),
    });
}
Hooks.on('getSceneControlButtons', addControl);