Note that phrase and NEAR search needs the positional information which may make the Xapian index file impractically large. GoldenDict will heuristically disable positional information when the length of document length reaches a certain limit.
"Available dictionaries in group" - here you can see how many dictionaries in the current group are suitable for full-text search, how many dictionaries are already indexed and how many dictionaries are waiting for indexing.
The dictionary will index for full-text search in background and started immediately after program start, name of the currently indexing dictionary is displayed in the status line. This process can take a long time and require many computing resources.You may turn off indexing for huge dictionaries like Wikipedias or Wiktionaries in preferences. To find dictionary which can't be indexed check GoldenDict with `--log-to-file` or check `stdout`.