As OP mentioned, inline code can be highlighted. The method still works:
- Go to https://example.com/admin/customize/themes/1/common/scss/edit (regarding your theme URL may differ)
- Go to the bottom of the CSS section and paste the code below:
p>code, li>code {
color: #c7254e;
background: #f9f2f4;
padding: 2px 4px;
border-radius: 2px;
}
Save. Done. Your inline text looks like this: ![]()
this is for code blocks only (picture below). The original question was about inline text

