I have a modified version of KiField that lets you show/hide component fields in a schematic. It can be installed with the command:
pip install -U git+https://github.com/xesscorp/KiField
In the spreadsheet, prefix a field value with "[I]" to make it invisible. Prefix it with "[V]" to make it visible.
Prefixing the header of a column with "[I]" will make every entry in that column invisible. Prefix with a "[V]" to make them all visible. Any values in the column prefixed with "[I]" or "[V]" will override the column heading.
Without prefixes, any new field is invisible by default. Existing fields retain whatever their original visibility/invisibility was.
New fields are given a position above the part reference. Existing fields retain whatever position they had.