You can use APIs to access object tags and to add or remove them:

To access object tags:

tag2 = DataModel.ObjectTags[2]
for tag in DataModel.ObjectTags:
name = tag.Nam
objects = tag.Objects

To add or remove object tags:

tag = Ansys.Mechanical.Application.ObjectTag("supports")
tag.Objects = [obj1, obj2, obj3, ...]
DataModel.ObjectTags.Add(tag)
DataModel.ObjectTags.Remove( Ansys.Mechanical.Application.ObjectTag("loads")