I use Collection Studio for my banknotes collection.
Although I see that there are customizable fields, I wish we had a specific field for entering the respective catalog number. Actually we could have 2 fields:
"International Catalog #"
"Regional Catalog #"
For international catalog, the most complete and usual is "Pick" and so, it could be "Pick #" instead of "International Catalog #".
Many countries have their own catalog and so, it would be interesting to have a field for that too ("Regional catalog #".
Since this is a very important information when classifying the notes, I wish those fields be present in the tab "Banknotes" (first tab).
Those fields should accept alfa characters for example "182a".
I tried to use the fields "Index" and "External Index" but I believe that they are for other purpose.
This idea should extend to other collectibles which there are catalogs like "coins" and "stamps".
What do you think?