我想，在可视化模式下进行选择的最简单方法是将字符串 Package 到span中，然后使用editor.dom.select选择该span。

// We get editor's content, where 'editor' is a tinymce editor instance
    var content = editor.getContent();

    function selectText(start, end) {
    // We have start and end position of the text which we want to select
    // Then we wrap our word or frase between positions into span with unique id
    let content_with_span = content.substring(0, start) + '<span id="'+start+'_'+end+'">' + content.substring(start,end) + '</span>' + content.substring(end, content.length);
    // I keep the original 'content' variable outside, because in my case user can switch between various frases and when we switch to the next selection, we don't want to keep previos span in text

    // Return content with span into editor
    editor.setContent(content);

    // Create selection
    let selection = tinyMCE.activeEditor.dom.select('span[id="'+ start + '_' +  end + '"]')[0];

    // If selection exists, select node and move to it
       if (selection) {
          tinyMCE.activeEditor.selection.select(selection);
          selection.scrollIntoView({behavior: "instant", block: "center", inline: "nearest"});
       }
    }

对我很有效，我希望它能帮助到其他人。

下面是我基于上面的@tonyAndr解决方案使用的一组选择脚本。我用它来构建一个定制的拼写检查器。

<script>

    var content = '';

    function selectionSet(start, end) {
    
        // span vars with unique id based on the section of text
        var spanId = 'id="' + start + '_' + end + '"'
        var spanClose = '</span>'
        
        // grab a copy of the current content 
        content = tinyMCE.activeEditor.getContent();

        // wrap the section of text into the span 
        let content_with_span = content.substring(0, start) + '<span ' + spanId + '>' + content.substring(start,end) + spanClose + content.substring(end, content.length);

        // return the new content into editor
        tinyMCE.activeEditor.setContent(content_with_span);

        // select the span
        let selection = tinyMCE.activeEditor.dom.select('span[' + spanId + ']')[0];

        // if selection exists, select node and move to it
           if (selection) {
              tinyMCE.activeEditor.selection.select(selection);
              selection.scrollIntoView({behavior: "instant", block: "center", inline: "nearest"});
           };
    };
           
    function selectionClear() {
    
        // restore the previous selection (in my use case the user is not able to do other edits)
        //in the case of spellchecking - user has ignored the selected error
        if (content.length > 0) {
            tinyMCE.activeEditor.setContent(content);
            content = '';
            };

    };
    
    function selectionReplace(start, end, replace_with) {
    
        //in the case of spellchecking - allow for the selection to be replaced with a new word
        if (content.length > 0) {
            let content_with_replace = content.substring(0, start) + replace_with + content.substring(end, content.length) ;
            tinyMCE.activeEditor.setContent(content_with_replace);
            content = '';
            };

    };
</script>