Hi,
OK, I understand now what you are trying to do. In my system (BW 7.4 SP 8) I can get it as follows:
1. Choose Delta Process FIL0 or FIL1;
2. Then the field Generic Delta appears. Here you can choose one of the options: Date, Timestamp, Timestamp Long or Numeric Pointer;
3. If you choose e.g. Date, then you will see the Delta Field, etc.
If it does not work this way and the field Generic Delta does not appear, then you can try to change the Delta Process from FIL0 to another value and back. You can also try it with a new DataSource.
If it does not work in any case, then it could be a bug. In that case please provide your BW release and SP level.
Best regards,
Sander