Easy way to simply format text on estimate/invoice

Hello. Is there an easy way to use basic html to format (for example) the payment terms in estimates/invoices? I have found the tutorial regarding css on invoice customisation, and I do understand about using css in webpage design, however if I just want to make some of the text bold for example, is there an easier way to do this? I have found the article on Rich Content Support which lists the html tags that are available, however I can’t find out how to actually apply them. Thank you.

pick any online html editor and format your text , copy html codes and paste , it should work
example

this text is bold

this is italic

this is italic bold

<p>this text is <strong>bold</strong></p>
<p>this is <em>italic</em></p>
<p>this is <em><strong>italic bold</strong></em></p>

That is what I have already tried - using basic html as per your example - but if I copy that into the invoice customisation template I just see the text including the tags when I create a new invoice/estimate. Is there somewhere else that I am supposed to type it? I’m sure that I am missing something very basic here.

It will show raw html codes while drafting invoice/estimate but when you save and preview you will see actual effect