XMLType isn’t supported very well by the OCI when in Unicode mode (which is what Toad uses), so Toad can’t support it very well either.
When you create an XMLTYPE column like that, without specifying ‘store as binary’, or ‘store as clob’, it will default to binary. Toad can handle it in a read-only fashion as clob, but not at all as binary.
You can cast your binary XML column to clob this way:
select m.ID, m.DOCUMENTO.GetClobVal() as DOCUMENTO
from my_table m;
If you find your table in the schema browser and look at the data tab, Toad will automatically query your table like this and you should see the data in a read-only fashion. If you want to query it in the Editor, you should add GetClobVal() yourself.