Advanced Braille Input Mode suggestions

[AAClause]

I received several suggestions about the Advanced Braille Input feature from a user. Here they are:

• avoid/detect duplicate entries in the dictionary
• add the possibility to define replacements for a specific input braille table

• allow the use of custom prefixes to temporarily translate with a specific braille table. E.g.:

  Custom prefix: ⣗ Braille table to use: Russian computer braille (ru.ctb) Advanced input entry: ⣗⡎⠷⠑⠱⠾ Result: Съешь