Yes you can. In the actions.xml, define it as a pop up window
<command class="" method="execute" windowType="popup" url="/wtcore/jsp/ext/mitg/someaction.jsp"/>
I added a URL link in the Library context. When I open the Link it opens in the same web browser as Windchill. I can't back out of it to go back to Windchill, so I have to close the Link and it closes the Windchill session also. I would like to have the URL link open in a new window or tab so it does not interrupt my Windchill session.
It seems like that is not possible. Instead it is an end-user training thing. Need to middle-click on the link. Then it will open in a new tab. Just basic browser management. Can't force it using Windchill bookmarks (aka links today).