You are trying to create a custom calculated key figure and you are unable to find the fields in the data source to perform the calculation.
C4C and Business ByDesign
Reproducing the Issue
1. Goto Business Analytics Work Center
2. Design Key Figures
3. Click on 'New'
4. Maintain the name and select the data source in which you would like to create
5. Select > Calculated Key figure
6. Click on Next
You will not find all the fields in the data source but it will show only the key figures available in the data source to perform calculation.
You can create calculated key figure only using the key figures available in the data source as they are quantifying values. Characteristics will not be seen in this tab calculated/restricted key figures since you cannot perform calculation on those fields.
This is system designed behavior. You can make use of key figures available in data source to perform calculation.
If the characteristics that you want to make use in creating calculated key figures are date fields then those fields can be created as key figure from Cloud Studio by partners. Then you can be utilize those date fields for creating calculated key figure. You refer to link for the steps to be followed while creating from Cloud Studio:
cannot create key figure, , KBA , cannot create key figure , fields missing to create calculated key , missing fields to create calculated kf , AP-RC-ANA , C4C, ByD, Travel: Analytics Tools & Frameworks , Problem