Thyristor SCR gate trigger
It does not say that you should apply 30V to the gate- it says the drive circuit should produce at least 30V with the gate disconnected. A current source with 30V compliance would satisfy that, and a resistor from a voltage source of 30V would as well. If you do not exceed the recommended drive current, the gate voltage will not exceed the maximum.
Applying excessive gate current using the back porch will increase gate dissipation, so it is not recommended. More than 100 microseconds at 30W exceeds the maximum. If you are supplying 2A Igm and the gate voltage rises to 15V then the dissipation is 30W.
Some kind of pulse shaping network can be used with a driver to create these waveforms, perhaps through a pulse transformer.