If you are a seasoned astrologer then you will instantly understand the value of Io Converter software.
You have a lot of charts - and now you would like to look at some or all of those charts from some different perspectives - it may be just moving charts from Tropical to Heliocentric or Sidereal.
You may want to change House Systems. If you have to do it by hand, one at a time it can take, well . . . forever.
If you have Io Converter you can do it fast and efficiently and without all the frustration of one-at-a-time processing.