By default, when you add new columns to a table, this does not affect the width of existing columns. The table's width is instead increased by the width of added columns:
But if retaining the current table's width is important, you can add new columns without increasing the table's width. Of course, in order to achieve this, the width of some of the existing columns needs to be decreased in order to provide space for a new column. So you have to tell Atlantis which columns to narrow before adding a new column. You can do so by selecting those columns before adding a new column.
For example, let's suppose that we need to add a new column to the table below, and the "Activities" and "Person in Charge" columns are the ones to provide space for a new column:
So you should first select the "Activities" and "Person in Charge" columns:
Then click above the vertical border where a new column should be inserted:
As a result, the space for a new column would be taken from the "Activities" and "Person in Charge" columns. The other existing columns would not be affected, and the table's width would remain unchanged:
You can select any combination of existing columns that should provide space for a new column.
You can select a single column:
You can select a noncontinuous group of columns:
You can even select entire table: