You are unlikely to need it right away, but since it is the next one in the row, you may ask what does it do.

This button lets you insert a set of variables that correspond to ease allowances in most templates. The available options of the sets of ease allowances depend on (1) size group and (2) type of the garment.

For example, for a comfortable dress your choice would be as follows:

The code on the right was inserted in the pattern scenario, at the current position of cursor, after I clicked the button comfortable. If you click another button, say fitting, a new set of variables will be inserted, in this case after the first set. The ease allowances will thus be overridden and set to the latest values inserted.