If you need to edit HTML of the template (for example, to modify image, add a table, change fonts, etc.) then you can use HTML editor directly inside Gmail compose window.

Here ere is how to do it:

1. Compose your email and click the “Insert Template” button on your Gmail to select from pre-made or customized templates:
   

2. Select the template you want to use by clicking on the image:
   
3. The template will load in your Gmail. Click on ‘HTML editor’ icon in the ‘Compose Email’ toolbar:

   

4. The new window with HTML editor and preview will open:
   
5. Click ‘Save and Close’ icon in the Gmail HTML Editor page to save HTML changes:
   
6. Change subject of your Gmail draft – the subject of the draft will be the name of your template
7. Now save a new template by clicking the “Save Draft As Template” button:
   
8. You will be asked where you want to save created template:
   
9. You will get a message that your template is being saved:
   

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