我在代码中做了一些更改，并使用absolute使弹出窗口可见。

:root {
  --VeryDarkGrayishBlue: hsl(217, 19%, 35%);
  --DesaturatedDarkBlue: hsl(214, 17%, 51%);
  --GrayishBlue: hsl(212, 23%, 69%);
  --LightGrayishBlue: hsl(210, 46%, 95%);
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: "Manrope", sans-serif;
}

body {
  background-color: var(--GrayishBlue);
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  padding: 20px;
}

.container {
  display: grid;
  grid-template-columns: 2fr 3fr;
  max-width: 1150px;
  max-height: 390px;
  margin: auto;
  background-color: white;
  border-radius: 0.8em;
}
.container:after {
  display: block;
  content: '';
  clear: both;
}

.img-box {}

.img-box img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.text-box {
  padding: 8%;
}

.text {
  padding-bottom: 30px;
}

.title {
  color: var(--VeryDarkGrayishBlue);
  padding-bottom: 10px;
}

.subtitle {
  color: var(--GrayishBlue);
  font-size: 1.1em;
}

.writer img {
  width: 50px;
  height: 50px;
  border-radius: 50%;
}

.footer {
  display: flex;
  flex-direction: row;
  align-items: center;
}

.name {
  margin-left: 12px;
}

.name h4 {
  color: var(--VeryDarkGrayishBlue);
}

.name p {
  color: var(--GrayishBlue);
}

.share {
  margin-left: auto;
  position: relative;
  padding: 20px 0 0;
}

.share-icon button {
  border: none;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background-color: var(--LightGrayishBlue);
  cursor: pointer;
}

.share-option {
  width: 250px;
  height: 40px;
  background: var(--VeryDarkGrayishBlue);
  border-radius: 10px;
  color: white;
  position: absolute;
  bottom: 100%;
  right: 50%;
  transform: translatex(50%);
  visibility: hidden;
  opacity: 0;
  transition: visibility 0s, opacity 0.5s linear;
}

.share-option:after {
  top: 100%;
    left: 50%;
    border: solid transparent;
    content: "";
    height: 0;
    width: 0;
    position: absolute;
    pointer-events: none;
    border-color: rgba(136, 183, 213, 0);
    border-top-color: var(--VeryDarkGrayishBlue);
    border-width: 10px;
    margin-left: -10px;
}

.share:hover .share-option {
  visibility: visible;
  opacity: 1;
}

<main class="container">
  <div class="img-box">
    <img src="/images/drawers.jpg" alt="" />
  </div>
  <div class="text-box">
    <div class="text">
      <h1 class="title">
        Shift the overall look and feel by adding these wonderful touches to furniture in your home
      </h1>
      <p class="subtitle">
        Ever been in a room and felt like something was missing? Perhaps it felt slightly bare and uninviting. I’ve got some simple tips to help you make any room feel complete.
      </p>
    </div>
    <div class="footer">
      <div class="writer">
        <img src="/images/avatar-michelle.jpg" alt="" />
      </div>
      <div class="name">
        <h4>Michelle Appleton</h4>
        <p>28 Jun 2020</p>
      </div>
      <div class="share">
        <div class="share-icon">
          <button><img src="/images/icon-share.svg" alt=""></button>
        </div>
        <div class="share-option hidden">
          <span>Share</span>
          <a href="#"> <img src="/images/icon-facebook.svg" alt=""> <a/>
            <a href="#"> <img src="/images/icon-pinterest.svg" alt=""> <a/>
              <a href="#"> <img src="/images/icon-twitter.svg" alt=""> <a/>
        </div>
      </div>
    </div>
  </div>
</main>

我认为没有javascript你就无法做到这一点。
你可以把你的共享选项（绝对位置）包含在共享图标（相对位置）里面，这样选项就会相对于按钮定位。

<div class="share">
                <div class="share-icon">
                    <button>
                        <img src="/images/icon-share.svg" alt="">
                    </button>
                    <div class="share-option hidden">
                        <span>Share</span>
                        <a href="#"><img src="/images/icon-facebook.svg" alt=""></a>
                        <a href="#"><img src="/images/icon-pinterest.svg" alt=""></a>
                        <a href="#"><img src="/images/icon-twitter.svg" alt=""></a>
                    </div>
                </div>
            </div>

和CSS

.share-icon {
            position: relative;
        }
        .share-icon button {
            border: none;
            width: 40px;
            height: 40px;
            border-radius: 50%;
            background-color: var(--LightGrayishBlue);
            cursor: pointer;
        }
        .share-option {
            width: 250px;
            height: 40px;
            background: var(--VeryDarkGrayishBlue);
            border-radius: 10px;
            display: flex;
            justify-content: center;
            align-items: center;
            color: white;
            position: absolute;
            top: -40px;
            z-index: 100;
        }

现在的问题是期权在相对期权的边界上，所以期权不能向右扩展！
我认为这个容器是有响应的，意味着大小可以改变。所以我认为唯一的方法是把选项放在主体中（不显示），当点击（或悬停）按钮时，你可以使用display flex来获取按钮的位置并将选项放置在它的顶部