By design, calculated columns cannot be inserted into other tables. You will also not see them in the list of columns available for pivot and unpivot. This is intentional and you can get around it by creating calculated columns through Insert, Transformations, Calculate new columns. When the column is created this way, rather than through Insert menu, Calculated columns, it will be available in those dialog boxes.
Here is the reason why:
The user may not be aware of it, but Spotfire performs a series of operations when opening and updating the DXP file, and those operations occur in a very specific order. The program is based on code after all, and code doesn’t happen randomly. When a DXP is loaded, the first thing that happens is the data is queried from its source. Then, transformations are applied, and they are applied in the exact order that the user created them. Thus, if a user adds a data table and then adds a change column name transformation, any future or subsequent transformations will involve the new column name, not the old. Furthermore, transformations take place when the DXP file is opened and when data is reloaded, and those are the only times they take place. In contrast, if the user inserts a calculated column, that column can be updated any time a value used in the calculation changes, which could be any point in time. That is why users cannot use inserted calculated columns to join. If you could, then the data load process would have to be performed any time a calculated value changed (to update based on the join) and that would simply bog down the program.