Can electromagnetism be used to generate gravity?

Assuming you are asking if a gravitational field can be switched on/off by flipping a switch in an electrical circuit, I think the answer is No.

The electromagnetic energy which you create must come from some other form of energy, which also gravitates. You are merely exchanging one source of gravity for another. At best you are moving the gravitational field from one place to another, in a finite time, like moving a mass.

A particular arrangement of current and voltage is not necessary. Any form of energy is sufficient to do the job.

Nothing feasible could be done by this method which could not be done more efficiently by bringing a mass to the required location. Even matching the feeble gravitational field of a 1kg mass would require an energy of $9\times 10^{16}$J, which is approximately the UK energy consumption for one month.

Yes, just as you say, the EM field tensor produces a stress-energy, which is the source of gravitational effects.

A charged black hole does have a different gravitational field then a non-charged one.

Now you are asking whether this can be used for creating a gravitational field. Yes it is possible, but if you check the EM field tensor, and the stress-energy it creates, then you will realize that to create a certain amount of (usable) stress-energy that can be used technologically (as a source of gravity), you would need to use so much EM charge, so much energy, that will not be effective.