I've already mentioned that, out of all the no-code tools I've used, my favorite is the Outline Headings feature of the Web Developer extension for your browser. This particular feature is my top pick for building templates because of its ability to show you how a webpage is organized from an overview perspective (with headings), in a simple manner, and without any clutter or preconceived notions. When using this method to conduct a website audit, if you identify a poor heading structure on a website, there is likely to be a negative effect on the website's SEO as well. I've personally found numerous examples of a single landing page with five H1 tags or having an H4 tag immediately following an H1 tag, many, many times while performing audits using the Outline Headings feature. For non-technical individuals, this method for conducting audits makes it easy for them to see problems in the heading hierarchy and communicate these issues with developers as a fixed solution using the Outline Headings feature. If you do not want to use the Outline Headings feature in the Web Developer extension, I recommend you use the Inspect Element function in conjunction with pressing Ctrl + F to search for.
What method we prefer for checking heading tags is using Ahrefs browser extension. All you need to do is open the web page and click the Ahrefs icon, then click the Content button you will find all heading tags under Content section. The reason we use Ahrefs extension is it is simple enough. You don't need to click the Inspect button to go for raw HTML file and open all folded elements. In addition, Ahrefs extension gives Meta information and even word count, which makes us checking basic information of a web page faster and clearer.