Re: the line
| 0006 | WKWNG | 04 | 714 | W | P0006-BEGDA=P0008-BEGDA |
what this tries to do is to set the IT 6 start date as IT 8 start date; not the other way. As per what you have said, you want to copy/create an IT 8 for the IT 6 date. The above line can not do that.
It needs to be the other way
| 0006 | WKWNG | 04 | 714 | W | P0008-BEGDA=P0006-BEGDA |
Also normally IT 8 should be copied from a previous record with any change as required. Instead of inserting using INS, I suggest using F as Indicator for step to call a routine (or form in a program) to do any validation, find the correct record that has BEGDA <= P0006-BEGDA, copy it and change as required.
Dynamic actions can not do any calculations, nor do any selection of a record when there are several IT records. For this and complex validations, you need to use function call
Also as Rahul said, it would be better to use 06 as Function character of step.