Need to add custom fields to exportmetadata csv file

In assets UI we have added few custom columns in list view. when we select on any article and then click on export metadata it will export those columns of that article into csv. so we are not able to get the custom columns added into csv.
Here are the list of columns in list view.

Here are the list of columns in the exported csv

So, its showing only few columns in the exported csv. we want all the custom columns to be added into that csv and also remove unwanted columns while exporting.