Please add the following two to KeyBoard Keys option of Trigger Predefined Action.
It's not a smart solution, but I was able to register my Eisu / Kana key in the following ways:
[BetterTouchTool] Add Keyboard Shortcuts "Shift+Option+Command+T"
[Karabiner-Elements] Complex modifications > Add rule > For Japanese (日本語環境向けの設定) > "コマンドキーを単体で押した時に..." Enable
[BetterTouchTool] Add "Send Keyboard Shortcut" to the item (Shift + Option + command + T) set in step 1.
[BetterTouchTool] Press the command key in the shortcut input form
[Karabiner-Elements] Remove "コマンドキーを単体で押した時に..."
You will not see the configured shortcut, but you can assign the Eisu / Kana key this way.
Yes, that's right. I use HammerSpoon.app to do the same thing, with F17 and F18 corresponding to 英数 and かな, respectively.
After all, I would like to be able to do it with BetterTouchTools alone.
The other method is to send the keycode directly using AppleScript, which can be done with BetterTouchTools alone, but it will slow down the response.
I have prepared presets so that you can easily use the "Eisu" and "Kana" keys.
Allows you to use the Japanese keyboard "Eisu" and "Kana" key.
This is a preset with keys that can only be entered on a Japanese keyboard. This is useful for people who want to use the "Eisu" and "Kana" keys on a keyboard other than Japanese.
[Japanese IM Key]
Press only Left Command key: Eisu key
Press only Right Command key: Kana key
Press Shift + Right Command key: Shift + Kana key
[Japanese IM Keys 2]
In addition, disabled triggers are provided so that you can easily assign the "Eisu"…
I think it will be useful until BTT officially supports "Eisu" and "Kana".