In most cases, there is only 1 tab per fixture model and mode.
The tab is automatically duplicated when there are different modes (= number of DMX channels) for the same fixture in the show (normal because the DMX chart is not the same).
In your example, it seems that the "led bar 34 vintage" fixtures have been patched with different modes.
In the current version of Daslight 4, I think it's not possible to rename the fixture tabs, as there is no right-click option to do so, nor any working double-click.
Maybe it's a feature that will be added by the developers.
A workaround is to clone the ssl file under a different file name in the fixtures library.
The name that appears in the tab is that of the ssl file.
Hope this helps.