Can the values of 2 or more fields be combined in a single field?

Please refer to the Wiki Documentation for the complete Field types reference.

Set the Type for the field that you want to store the combined value to “Fixed”.

In the template setting for that field, you can enter the keyword %FIELD#% (where # is the field number) and the keyword will be replaced with the value of the designated field when it is saved.

For example, to combine your first 2 fields into third, inserting a comma between them, set the template for field 3 to:
%FIELD1%,%FIELD2%