When you are looking for a document under the 'Search documents' section, you can use the field 'Text Search'. This field follows the ORACLE TEXT specification: https://docs.oracle.com/database/121/CCREF/cqoper.htm#CCREF0300
The reserved words should be avoided because if you use one of these words you will get an error and no documents will be found.
Reserved words: 'about','accum','and','bt','btg','bti','btp','equiv','fuzzy','haspath','inpath','mdata','minus','near','not','nt','ntg','nti','ntp','or','pt','rt','sqe','syn','tr','trsyn','tt','within'.