Hi @Tomas
Welcome to Forum and Thanks for posting 
Could you please share your code and the Error info here?
I will share sample code below which is completely working fine in WF Studio,
<robot driver="chrome" close-on-completion="true" maximize-on-startup="true" name="chromedriver" start-in-private="false">
<script><![CDATA[
myarr = new ArrayList();
myarr.add("https://www.google.com/");
myarr.add("https://www.geeksforgeeks.org/");
myarr.add("https://automationacademy.com/");
for (mylist in myarr) {
open(mylist); //Either This line too...
openLinkInNewWindow(mylist);// This line works too...
}
]]></script>
</robot>
If this is not what you are looking for, then please share me your code and error information to have a look at it.
Thanks for posting