I need advice on declaring tax deducted on dividends for shares I hold?

For local dividends you have already paid the tax, there isn't a place for them yet, usually you receive an IT3b from the company or fund, but you do not need to worry as it has been paid for you.

That is good and well but is not reflected as such anywhere in the eFiling system that I am aware of.

Yes, because SARS has not created a place for it on the ITR12 yet. You do not need to add in anything, the tax has been paid and everything settled.