NT doesn't read two futures with same name but different point value.
In other words, NT goes in conflict whith same underlying mini sized.
Said that, in order to see FTSE Mib Future, u must register two different instruments as following:
1\ Instrument Editor => new ...
Master Instrument: FTMIB
Instrument Type: Future
Tick Size: 5
Point Value: 5
Session: Idem
Description: ... what u prefer
Exchanges: Idem
Misc: Interactive Broker: FTMIB|||5
then
2\ Instrument Editor => new ...
Master Instrument: FTMIB1
Instrument Type: Future
Tick Size: 5
Point Value: 1
Session: Idem
Description: ... what u prefer
Exchanges: Idem
Misc: Interactive Broker: FTMIB-disabled|||1