I fill out missing information letters and often required material is missing
from more than one field. I want to be able to fill in the explanation for
missing information in field 1 and field two into the same cell, which
content will be merged into a letter.

Right now, I can use =A1 to fill up the cell with an explanation found in
A1, but I can't reference more than one explanation to the cell.

I've tried =A1, A2 to get explanations to multiple fields in one cell, but
it doesn't work. Concatenate function doesn't work either.

The easier the better.