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=""
  

• 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

If I want to check if current cell is empty this is working for me:

=ISBLANK(INDIRECT(ADDRESS(ROW(),COLUMN())))

The cell at the previous row in the column will be

=ISBLANK(INDIRECT(ADDRESS(ROW() - 1,COLUMN()))) etc.