You will need to have both Elementor and Elementor Templater plugins installed and activated.
Elementor Templater will supply the required blank template, the CSS and the js for everything to work.
Create your page as normal making sure to insert the nachor menu widget in the appropriate places.
If you are using a pre made template make sure to insert a full width section at the very top of the page before inserting the temaplte. This will serve as a plpaceholder for our menu when we come to insert it later on.
When you are happy with everything make a note of the names of your anchor menu and having saved your work, exit the editor back to the dashboard.
Now proceed to Appearance >> Menus to create your menu. Using the Custom Links section insert each of your anchor menu name proceeded by the # key i.e. #anchorname and add it to the Menu. When all anchor names have been added save your menu but do not attach to a theme specific menu location.
Continue in the putting it together tab!
Navigate back to the Elementor editor screen. Now drag and drop the Columns widget inside the Section we created earlier at the very top of the page. This will 2 columns but we only need on so go ahead and delete one of the columns.
In the side panel scroll down and locate the WordPress Custom Menu widget. Drag and drop it in to the column we created above and Elementor will automatically open the settings for you to select the Menu item that you created in the process section.
Although Elementor will also open its inbuilt settings, some of them may not have the intended effect depending on your theme of choice but you should be able to use most of them.
Lets take a look at some of the Caveats!
This is a new feature and as with all things new, there's going to be some caveats that will require some adjustments.
Currently you will need to insert a class named "anchor-menu" in the Advanced tab of the Column part of the very first Section you created at the beginning - the 2 above!