Try this:
- Open the List Panel for the schematic library. At the top select "All Objects From All Components".
- Right click in the List Panel, select "Choose Columns", and set "Parameters" and "Parameter Names" to display.
- Now click at the top of the "Object Kind" column to sort it alphabetically
- Go down the list to "Parameters" and select the ones you want to change using the regular Windows way of selecting items with Ctrl Click, or Shift Click, etc.
- Now go to the Schematic Inspector Panel. At the top select "All Types of Objects from All Components".
- Go down to "FontID" and click on it. An elipsis will appear on the right side of the item line. Click on it.
- You will now see the Windows dialog to change the Font. Make your changes and hit "OK"
- Save your library.
The only alternatives to the above are one-by-one changes, or you could write a script to do the global change.