How to enable editing of a single cell in a table

In a table, the user must be able to edit the values ​​of each cell in a specific column.
The current solution is using a dropdown menu of multiple selection, but the user has to scroll through the options, which is a bit inconvenient.
The current solution

The table is wide, and the insertion of a button in the cells is a problem.
adding a contextual button on the table is an option, but that means that the contextual menu has to be fixed, and it could be a problem since the menu that is above is not fixed. Once the button is activated, a pop-up window with the cell configuration will appear.

The complete table

Can you recommend a conventional method to enable the editing of a single cell?