Customize Cells with their own Prefix or Suffix
Format a cell or group of cells, rows, or columns so that when a number or any text is entered into subject cell(s) a prefix or suffix will appear next to (in front or behind) that number or text. eg. "31 Amps" or "11 Hrs" or "101 km/hr"
Maybe in the "custom" field of "Format Cells", there could be an "Add Custom Prefix" and "Add Custom Suffix" button which allows entry of the required Prefix or Suffix.
Michael Bryson commented
You can do this with custom number formatting. However, this only works with numbers and not with text.