Is there a word for the commonly used given name of a person?
The classic Falsehoods Programmers Believe About Names list is always worth a good review.
Based on the comments, there is no direct equivalent in the English-speaking world to the concept of tilltalsnamn. In general, one's first name (ie. first given name, forename) is used for both address and for legal purposes, and any variation from that is an exception. Certainly, many people choose to go by a middle name, or another name, but there is no special status accorded to this name and no specific term that is universally used.
Something similar you may find in a CRM system, human resources file, or the like might be addressee or addressee name, the name that would be used to populate letters and mailings. For example, you would use Mike DeWine or R. Michael DeWine and not Richard DeWine or Richard M. DeWine if writing the current governor of Ohio.
Another common formulation is preferred name, i.e. the name one prefers to be known by. This need not have any relation to any part of the official name, however. Furthermore, someone might prefer different names in different scenarios— Mary Catherine Gallagher, MD might be
- Catherine Gallagher in day-to-day life
- M. Catherine Gallagher on her medical license
- Cat on her business card
- Katy on her nametag at her high school reunion
- Skeeter on her nametag at her sorority reunion
Example 6 would be a nickname, and many would consider 3 and 4 to be nicknames as well, but 1 and 2 would not be called nicknames, so it would be a poor mapping to the Swedish term.
If one must get down to this level of specificity, one must be specific when labeling: Name as it should appear on your name tag, Name as it should appear in the list of sponsors, etc.