How to address the current cell in conditional format custom formula?

The current cell is addressed by the first cell of a range in the conditional formatting. In your example, the range is A4:M10 and therefore you can use A4 as “current cell”.

• Check for empty content:

  =A4=""
  

Relative vs absolute references in conditional formatting work just like copying a formula.

• Check that the cell in 2nd row of current column row is today:

  =A$2=TODAY()
  

• Combine using AND operator:

  =AND(A$2=TODAY(), A4="")
  

I have updated a copy of your example spreadsheet – https://docs.google.com/spreadsheets/d/1MY9Jn2xpoVoBeJOa2rkZgv5HXKyQ9I8SM3kiUPR9oXU/edit#gid=0