Hi Patrick,
Before you jump the guns to change the filed characteristic to make it editable either using screen filed setting in T588M, could you please first check your requirements. take this to basics and check below before you change any setting.
1. why are you creating quota manually(by using LSMW) can you not use SAP standard RPTQTA00.
2. has your quality system got most current data i.e payroll periods have been generated etc.?
3. if you insist creating quota using LSMW first try and create one single record manually, if you are not able to create record via pa30 that means your recording will not work (that seems to be your problem here as the filed p2006-ANZHL is not letting you create record due to error mentioned above for which I would ask you to read post below by Kuppan.
4. understand you system first before creating LSMW script is your quota created by Time management if yes this filed will not be editable (in most configured system I have seen)
Solve creating one record then only your LSMW will work. I hope this info will be useful don't create your self issues by changing config where it might not be required at all, understand you system behavior and config before you change anything
KR
Sid