Hello Susanne,
That’s a lot of attributes, so it makes sense you want students to delete them. Deleting each one separately is the most straightforward way to do this within CODAP. You, and they, may find it a bit easier to use the case card instead of the case table.
As an alternative, import the Choosy plugin into the document containing the data using this url: https://codap.xyz/plugins/choosy/
Go to the Attributes tab of Choosy and in the gray stripe next to none press the closed eye to hide all the attributes. (See image below.) Then click the slider next to each of the attributes you wish to keep. Voilá, you’re done and can close Choosy.
The downside of this method is that the data values of all the hidden attributes are still present in the document, just hidden. This means that the document isn’t any smaller than when you started, in contrast to the first method.
Hope this helps,
Bill