To turn a text link in Accordion Block to Button, you can follow these
#1. First, find the Accordion Block ID. Use below tool.
In my example, it is:
- #block-yui_3_17_2_1_1722754225107_12085

#2. Next, identify the URL inserted into the text.
In my example, the URL is /book-now

#3. Use this code to Custom CSS box
#block-yui_3_17_2_1_1722754225107_12085 a[href="/book-now"] {
background-color: #000;
color: #fff;
padding: 5px 20px;
display: inline-block;
font-size: 16px;
margin-top: 10px;
border-radius: 10px;
}

#4. Result
