To make text bold in forms that allow use of HTML, you must use what are called 'Bold tags' that are constructed as follows:
<b>This text will render as bold in a form that allows HTML</b>
To explain further, you must start by adding an open bold tag, then insert the text between this open tag and the close tag that will be made bold.
Open tag: <b>
Close tag: </b>
E.g. I only want <b>this</b> word to be bold. (In the example, only the word "this" would appear bold)
There is a third party resource that explains this in greater depth - https://www.w3schools.com/tags/tag_b.asp
Please note that if you build your form using HTML, we do not directly support any issues this code may cause, so there is a risk in using it.