I'm not sure if there is any way to remove the "linked subset" property.
You could first create subset of the linked table and then you can close the linked table.
The only way that I know of to break the link, is to save the table, close the table, then open the table, and the link will no longer be in place.
Sorry Holger, don´t know a better solution either. 
Summary Tables and Subsets have an option to "link" the new table to the original data table.
"Data views" have such a link enabled by default.

Cool:
Row Selections and changes to the values are automatically linked between the tables.
But sometimes one needs to remove such a link
- to add additional rows to the main table
- to rename columns of the linked table
...
Links cannot be saved, so, one can save the tables, close both tables and open the "linked" table again - without the link.
Is there a faster way?
a right click on
doesn't seem to be the right way ...