If I do create a sub domain it appears in the list of domains
and If I delete it from there it does removes Not only sub domain I wanted to remove but also the Main domain
If u see it and decided to remove it (like some test sub domain so far)
u click it in the domain list and u'r getting in the interface of Main Domain
IF you'r not too careful and think that clicking sub domain must get you in the area of sub domain management where you can remove the sub domain then first think you see is an remove button
So kind of tricky, if u heat it domain is gone
IF the interface change is too difficult , I would us some transitional option like a trash ,