Currently Content Translation organises the content in three columns of the same width (source, translation and tools) . While source and translation content columns can always benefit from more space, the tools column just needs enough space for the cards to fit comfortably. Making the tools column to stop getting wider when it reaches a certain point can help to make better use of the available space.
For screens wider than 1200px, we don't need the tools column to get wider. At 1200px wide screens, the tools column is 400px wide, and it can remain that way for larger screens too. That is, we want to limit the tools column width to 400px and make sure that the extra room is used by the content columns.