Assignment to feature & did not take place

What causes this issue?

You can assign a specific operation (assignment) to each decision
option within a feature. You can also define decision option ** whose
assignment is effected for all unlisted decision options (this is known
as a default value).
Example:
D PERSK
K1 &ABRKS=D1, <- D1 for employee subgroup K1
K2 &ABRKS=D1, <- D1 for employee subgroup K2
K3 &ABRKS=D2, <- D2 for employee subgroup K3
** &ABRKS=D0, <- D0 for all other employee subgroups
If you now create employee subgroup K4 and the default entry ** is
missing, the system is unable to find a decision option for payroll
area ABKRS.

How to fix this error?

Define a decision option for K4 or for default value **.

Error message extract from SAP system. Copyright SAP SE.