I need to drop i Commander who is not playing anymore
Open a support ticket at https://d3go.com/support/. They’ll demote an inactive (for 2 weeks I think?) commander at the request of another commander. The only exception is that they won’t demote the alliance’s founding member.
Also, it might not be 2 weeks if you are the founder. You can request to demote any commander as you wish if you are the founder of the clan. They will want you to submit a photo of your ranking on the leader board. I know because I recently did this for my clan. Hope this helps.