The approach suggested here doesn’t work - you can transfer flow variables to a table using the Variable to Table Row node, but the flow variables themselves still remain.
There isn’t a straightforward way to delete or remove flow variables (see previous forum discussion on this topic here: delete flow variable). As Iris mentions in that thread, a workaround might be to use the inherent local flow variable scope of components (previously called wrapped metanodes in the link) to effectively filter out flow variables created inside them.
Maybe there is a need for something like a “Flow Variable Filter” node. I would be interested to hear thoughts from others in the forum community about it.