TLDR; Backup the config, edit it and upload it to the FritzBox again.
Prequisites when using emojies or other more complicated unicode stuff:
- Set some setting to that unicode string and put something searchable ascii in front or behind it A new Wifi profile name for example
- Backup the config and search for the searchable ascii, there should also be the encoded unicode string which one can just past and copy elsewhere in the downloaded config
For example, 🪴 turns into
\\360\\237\\252\\264
How to:
- Backup the FritzBox config