It's to my understanding the field chooser dialog is not responsible for fixing/unfixing columns. Was this something that was previously working for you? If so can you please provide a screenshot of the area in which you want to address?
Let me know if you have any questions regarding this matter.
Thanks for the responds.
We have different screen in our application with Grid and FieldChooser, where it is working fine. For one screen it is not working.
The button is working fine in Grid, but not working with fieldChooser. Please find the screen shot below and let me know if any further information is needed.