Not possible to bind "<" key as a hotkey

The term for this keyboard is either an ISO keyboard (in contrast to the ANSI keyboard of most US keyboards), or a 105-key keyboard (in contrast to 104 keys on a US keyboard).

Searching those terms on these forums, it looks like aoe2 only quite recently fixed the issue.

Key 56 can be a hotkey but does not appear in hotkey list - Age of Empires II: DE / II - Report a Bug - Age of Empires Forum

Thankfully once reported it was fixed pretty quickly, so hopefully the same can be true here.