Hello,
Please note that the addDefaultStyles option prevents adding some styles. Also please note that the placeholder names to be replaced don't include the template symbols.
Please use the following code:
$placeholder = 'EXAMPLE';
$testValue = '<style>p {color:red; font-weight:bold;}></style><p>Test HTML</p>';
$docx->replaceVariableByHTML($placeholder, 'inline', $testValue);
All styles must be applied correctly now.
If you send to contact[at]phpdocx.com the template you are using, we can generate a custom code using it.
Regards.