I just pushed a new version to AnkiWeb that has better keyboard support. I want to properly document the new shortcuts, so I'm not triggering the update nag in Yomichan, but you guys can check out by re-downloading the plugin.
Ctrl + [1234567890] => Add term at N as expression
Alt + [1234567890] => Add term at N as kana
Shift + Ctrl + [1234567890] => Add kanji at N
Ctrl + [1234567890] => Add term at N as expression
Alt + [1234567890] => Add term at N as kana
Shift + Ctrl + [1234567890] => Add kanji at N
