Adding existing (transient) Entity to opened AureliusDataset

I would like to insert an existing, not persisted, entity into an AureliusDataset.

The Dataset could be opened with SetSourceList or SetSourceObject.

I tried to add the new entity by doing this:

Dataset.Insert;
try
Dataset.FillRecord(Entity);
Dataset.Post;
except
on Exception do
begin
cancel;
raise;
end;
end;

After testing this, I recognized, that FillRecord removes all Fields from FModifiedFields.
Posting the new Dataset will not "copy" the Fields filled by FillRecord.

How could I insert this Entity instead?

You should manually modify the fields, or add the entity to the list, close and reopen the dataset.