Here’s a short tutorial video without explanation. For some of you it might be better than a thousand words, while others can read on below.
To change the width of a column, select multi column element from the treeview on the right side of the email design. Then you should see double arrows between the columns, that you can drag to adjust column width.
If you want to be more precise with sizing, you can select each column one by one, using the Columns toolbox in the right column of the editor, and define the exact size for your column in pixels.
There are three properties under Column toolbox, which apply only to the selected column. If you wish to change these properties on another column, please click on the desired column (shown in grey in the toolbox) and click on it. Once you have selected a column, it will be shown in light blue.
Properties below the Visibility settings heading apply to all the columns, so use these only if you want to hide all the columns on mobile or desktop.
This is how you can do it in Chamaileons' editor: