connective N1 uncommon politewritten
とはいえ — even so
とはいえ
A full written guide for とはいえ is on the way.
This point is mapped in the grammar tree, but its examples, formation table and usage notes haven't been written yet. The fastest way to learn it now is to meet it in real sentences inside Jengo.
See とはいえ in real sentences
Jengo shows とはいえ the way you actually meet it: inside real Japanese sentences, so it sticks instead of staying an abstract rule.
Study it in JengoSources Compiled with reference to A Dictionary of Advanced Japanese Grammar.