It seems there is no possibility to disable global IP block by a wiki admin. It is especially annoying if the global blocks are set without special care (long time, wide IP range, including logged in users, etc.).
Tested today on the following case:
* Yesterday global IP range was blocked (it included PL WM toolserver IPs):
* Neither previous whitelisting:
* nor today attempt:
seemed to enable editing by logged in users from this IPv6 range.
After recent change of this global block
not-logged users still cannot edit from these IPs despite the local unblock above. (however this is not a problem, just case)