index.css

:root, body, #app {
    height: 100%;
    box-sizing: border-box;
    margin: 0;
}

body {
    padding: 8px;
}

#app {
    display: flex;
    flex-direction: column;
}

#app .top-box {
    margin-bottom: 10px;
    display: flex;
    align-items: center;
}

#app label:last-of-type {
    flex: 1 1 auto;
}

textarea#textBox, #previewBox {
    height: 100%;
    width: 100%;
    box-sizing: border-box;
    overflow: auto;
    font-size: 20px;
}

.button-box {
    margin-top: 10px;
}

::-webkit-scrollbar {
    width: 10px;
    height: 1px;
}

::-webkit-scrollbar-thumb {
    border-radius: 10px;
    -webkit-box-shadow: none;
    background: #A8A8A8;
    -webkit-box-shadow: none;
}

::-webkit-scrollbar-track {
    -webkit-box-shadow: none;
    border-radius: 10px;
    background: #eae9e8;
    -webkit-box-shadow: none;
}

.el-drawer__body {
    height: 100%;
}

.el-drawer__body .el-table {
    height: 100%;
    overflow: auto;
}