Populate a cell with a value simply by clicking on it

Hello!

I am creating an evaluation document. Each area has several traits that I look at. Each trait can be given a 4 (Highly Effective) to 1 (Ineffective) grade. Each grade has its own column, so instead of putting an "x" under the score for each trait or writing a 4, 3, 2, or 1 under each grade, I would like to click on the cell and have that score appear. I have attached a copy of the document with the company-specific information deleted.

If you open the attachment, let's look at Trait 1 of Area 1 (row 12). I would like to click on G12 and have a "4" appear. If I then click on H12, I would like the cell to show "3" and the "4" in G12 to disappear. I would like this ability to be installed for each trait, and for Observation 1 (columns G-J) and Observation 2 (columns K-N) to not affect one another.

Any help would be appreciated. Let me know if you need more information.