Update Navigation Settings of a List automatically , NO manually

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C#

automation

SharePoint2013

, +

Hi I tried to find a solution for this:

I'm using the Metadata Navigation settings of Lists in SharePoint 2013. They are drop down menus\filters that sorts my lists.

These menus are based on the values of Choice Type columns or Metadata Columns. My problem is that I want to update the values (filters) of these menus\filters automatically , without human intervention.
This means: If there is a new type of choice\metadata in the column , I want that the drop down menu would be updated automatically and with Choice Type columns this is not possible or I couldn't figure it.

I have to clarify that the insertion of the items in the lists is automatically with a tool called Layer2 so I can't insert values in Metadata Type columns.

Also I tried to create a workflow that insert values in a Metadata Type column" and then insert the metadata navigation menu\filter of the list based on this column BUT I check and looks like is not possible insert values in metadata columns though workflows.

Does anybody knows how to update the "Metadata Navigation filters\menus" of a list automatically?
I don't want add a new type of choice manually or new metadata manually.