My ~/.cache/xfce4/xfce4-appfinder/history cumulates duplicates over time. For example, one entry is like "bash ~/path/to/helper.sh", which appears several times in the cache file. As a result it is also shown as match several times during "Alt+F2" usage.

I think the concept of bash "export HISTCONTROL=ignoreboth:erasedups" should be implemented, just keep the last entry and wipe duplicate strings. Maybe leading and trailing spaces should be trimmed as well before deciding on duplicates and saving them to the 'history' file.

I'm running git.xfce.org#master since spring this year, I think this was always the case.