Question regarding Item Hierachies in PPS

Hi experts,

When trying to modify my current Hierarchy Template (IMG Activity => "Define Hierarchy Templates and Assign Transaction Types") I am facing the following error:

Hierarchy template ZHIER_SE still in use in active documents; cannot save rule

Currently, such Hierarchy Template is not assigned to any Transaction type...

How can I carry out any modification? Do I have to create a new one?

Thanks in advance and best regards

Vicente

PD: I have realized that I cand add new lines and modify existing ones but I am not able to delete lines in Define Item Type Control table.