Starts with() returns 0 or 1. If that is part of a formula that require character argument, that could explain the error message. However, Starts with() alone would not give that error if :Term is a character column.
In this case, the Word() function should work.
Paste this into a column formula
Or if you want to replace the values in the :Term column, try running this script (assumes there is always some text before "[")
For Each Row(:Term =Word(2,:Term,""));
Regex() can also be used and allows a more fool-proof search. However, here it requires some extra effort since \[ and \] have special but different meaning in jsl and grep.
But this should work:
Message was edited by: Marcus Sundbom