Clean and simple:
<form action="/myaction" method="post" target="_blank">
<!-- other elements -->
<a href="#" onclick="this.parentNode.submit();">Submit</a>
</form>
In case of opening form action
url in a new tab (target="_blank"
):
<form action="/myaction" method="post" target="_blank">
<!-- other elements -->
<a href="#" onclick="this.parentNode.submit();">Submit</a>
</form>