Ads a toggle in memrise.com to control the timer. You can click on the timer to pause/unpause the timer.

memrise-timer-toggle.user.js

// ==UserScript==
// @name           Memrise Timer Toggle
// @description    Ads a toggle to control the timer. You can click on the timer to pause/unpause the timer.
// @match          https://www.memrise.com/course/*/garden/*
// @match          https://www.memrise.com/garden/water/*
// @match          https://www.memrise.com/garden/review/*
// @version        0.1.2
// @grant          none
// @namespace      https://gist.github.com/AntonioRigo/fae2536dbf5b7626c509102b2226353c
// @updateURL      https://gist.github.com/AntonioRigo/fae2536dbf5b7626c509102b2226353c/raw/7e830938f94e4c4370e2e69c9f4a2142f008761e/memrise-timer-toggle.user.js
// @downloadURL    https://gist.github.com/AntonioRigo/fae2536dbf5b7626c509102b2226353c/raw/7e830938f94e4c4370e2e69c9f4a2142f008761e/memrise-timer-toggle.user.js
// ==/UserScript==

var onLoad = function($) {
    $("#left-area").append( `<p id="timer-switch">Pause timer</p>` );

    document.getElementById("right-area").addEventListener (
    "click", ToggleTimer, false
    );
    document.getElementById("timer-switch").addEventListener (
    "click", ToggleTimer, false
    );

    function ToggleTimer (zEvent) {
        if (MEMRISE.garden.timer.paused) {
            MEMRISE.garden.timer.unpause();
            document.getElementById("timer-switch").innerHTML='Pause timer';
            console.log('unpaused');
        } else {
            MEMRISE.garden.timer.pause();
            document.getElementById("timer-switch").innerHTML='Unpause timer';
            console.log('paused');
        }
    }
};

var injectWithJQ = function(f) {
    var script = document.createElement('script');
    script.textContent = '$(' + f.toString() + '($));';
    document.body.appendChild(script);
};

injectWithJQ(onLoad);