Variable cards can be saved to the deck just like analyses (see Saving, Exporting, and Sharing Analyses).
You can save a variable card in one of two ways:
Click the Save button in the upper-right corner. This will save the left-most variable card.
Hover over a variable card and click the Save button that appears below it.
Once saved, the saved variable card name appears in the deck. Click it to display it (this will open Card View if you are not already in it). Saved variable cards will be exported and shared along with the rest of the deck as described in Saving, Exporting, and Sharing Analyses.