Exporting Variables - how to?

NOTE: Prior to Reactor version 3.3, all variables were unconditionally exported. As of 3.3, exporting is user-configurable. The default for all new variables is not exported ; however, in order to maintain backward compatibility with configurations created prior to 3.3, the default for all existing variables (i.e. those created in versions 3.2 and earlier) is exported .

there is no how to in the documentation

Click the export button on the variable row. When highlighted green, the variable is exported. You also need to cause a change in the value of the variable to get the state variables created.

for those who need it