Bug
You should be able to resize columns.
You are not able to resize columns.
I'm not able to reproduce this problem: you can check my test example: https://codepen.io/msamsel/pen/ZXbPbJ?
You can also prepare your example which will show this problem, maybe I do something wrong in my example.
The problem occurs with the divarea plugin. The example you have is using an iframe for the editor.
I was able to repeat it in divarea. Thank you for the clarification.
Fixed in e3be5c1.
Most helpful comment
The problem occurs with the divarea plugin. The example you have is using an iframe for the editor.