Hi Michal,
Yes, I'm mainly talking about static subnets under "Manage Subnets & IP addresses".
If the subnets are contiguous and have the same subnet mask, (i.e. 172.16.1.0/25 & 172.16.1.128/25), they could certainly be merged or splitted with a single click as there wouldn't be any overlap between the two.
If merging a smaller subnet into a larger one (i.e. 172.16.1.0/27 into 172.16.1.0/25), then a wizard might be needed to review overlapping data.
Thanks!