Unable to customize Kana Key Table

[Yuri I. Kornilov]

Ubuntu 11.10
ibus-anthy 1.2.6-2ubuntu1

I cannot remap [~`] (upper left key in main area) key in ibus-anthy kana key table editor.
I'm trying to setup output char "ろ" for input chars "`" and "~", but this does not work.
It looks like Setup-IBus-Anthy silently ignores my settings.

PS. I am trying to setup IBus-Anthy kana layout for usual QWERTY keyboard. SCIM has ready-to-use so-called "101キーボード用かな配列" (kana layout for use with 101-key keyboard), but IBus does not. So I want to customise this layout by hand. For example, in 101-key kana layout [~`] key is used instead of the missing [ろ] key (which exists on 109-key Japanese keyboard). Romaji typing method is slow for me and is not an option.