I'll refer to the graphic you so kindly provided.
When choosing Formulas:Functions there are 852 entries. Then, searching for "convert" using Full Text Search (FTS) yields 162 entries.
Similarly, choosing Formulas:Text Formulas yields 232 entries. Then, searching for "convert" using FTS yields 68 entries. Alternatively, searching Text Formulas for "number" with FTS yields 137 entries.
All other options in the Help dropdown Formulas category (Operators, Math, Dates, Time, Boolean, etc) have significantly fewer choices, typically 25 or less.
It would help if an AND search could be carried out in the Help find field, or if a further subcategorization of the text functions could be implemented.