Looking for an Inline Text Editor with "styled tags"

I have already looked at a number of javascript based text editors and there are a number that offer WYSIWYG support for HTML and even a few for inline Markdown. However I am looking for something more specific and I wanted to ask the community if they have any experience with tools that could provide a solution.

Brief: A text editor that allows a mix of static and variable data input (example: Microsoft Word's "Mail Merge" feature). The variables should be added through an external action to the editor, and once added the text within the "tag" cannot be edited (although the entire tag can be removed or moved).

Target Audience: Non-developers that need to create and manage the source template with variables.

NOTE: I am not looking for HTML, but post-processing editor output might be OK. Ultimately the final output needs to be in a template style text format such as the Mustache.js style template below (tabs and newlines escaped):

Company: 
Address: 

,  

Phone: 

Obviously someone with basic Microsoft Word experience should not be expected to be able to write complex templates like this, so I created a mockup of what I imagine the interface might look like...

In the image below, the variables are being pulled from database but they could be from any source. This is also a much more advanced design but this is something that I would like to eventually implement that allows for conditional input (ship_address_2 and ship_country). This image also displays the optional tab ruler which will also be a future addition.

The overall project is written using Vue.js, and right now I only have a basic textarea input that I would like to replace.

Edit: simplified image to reflect more narrowly the scope of my question... and striped out the tabs and newlines from the mustache.js template example.

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