fastapi-admin/fastapi_admin/templates/widgets/inputs/editor.html

<link href="https://cdn.quilljs.com/1.0.0/quill.snow.css" rel="stylesheet">
<div class="form-group mb-3">
    <label class="form-label">{{ label }}</label>
    <input {% if not null %}required{% endif %} type="{{ input_type }}" class="form-control" name="{{ name }}"
           {% if disabled %}disabled{% endif %} value="{{ value }}" hidden>
    <div id="editor-{{ name }}">
    </div>
    {% if help_text %}
        <small class="form-hint">
            {{ help_text }}
        </small>
    {% endif %}
</div>
<script src="https://cdn.quilljs.com/1.0.0/quill.js"></script>
<script>
    Quill.prototype.getHTML = function () {
        return this.container.querySelector('.ql-editor').innerHTML;
    };
    Quill.prototype.setHTML = function (html) {
        this.container.querySelector('.ql-editor').innerHTML = html;
    };
    let toolbarOptions = [
        ['bold', 'italic', 'underline', 'strike'],
        ['blockquote', 'code-block'],
        [{'header': 1}, {'header': 2}],
        [{'list': 'ordered'}, {'list': 'bullet'}],
        [{'script': 'sub'}, {'script': 'super'}],
        [{'indent': '-1'}, {'indent': '+1'}],
        [{'direction': 'rtl'}],
        [{'size': ['small', false, 'large', 'huge']}],
        [{'header': [1, 2, 3, 4, 5, 6, false]}],
        [{'color': []}, {'background': []}],
        [{'font': []}],
        [{'align': []}],
        ['clean']
    ];

    let quill = new Quill('#editor-{{ name }}', {
        modules: {
            toolbar: toolbarOptions
        },
        placeholder: "{{ placeholder }}",
        theme: 'snow'
    });
    {% if value %}
        quill.setHTML('{{ value|safe }}');
    {% endif %}

    quill.on('text-change', function (delta, oldDelta, source) {
        $('input[name={{ name }}]').val(quill.getHTML())
    });
</script>