Business & farm

I just took a quick look.

It does not appear to be possible to efile the Form 1041-A. (You can get a six month extension BTW)

It does appear that you can efile the 1041 even if you need to mail in a 1041-A. But often the proof of being able to efile is very dependent upon your particular situation and you can't know for sure until you try.

I would not worry about the 5/15 lines. You have to use forms mode to fill out the 1041-a so it is trivial to right click on the amount field and choose "add supporting details"  (or control-i)

But if this is the only year you're filing this 1041, who cares? If you can't efile then just mail it in. (Send certified and keep the green receipt stamped by a USPS employee. No need for return receipt. Having that is proof of filing. (Technically it shifts the burden of proof to the IRS to produce, say, the envelope without a return in it. In practice they cannot do that.)