Customizing the Opportunity ListColumns in other modules

[radu]

You have to modify the example in the documentation with your own definitions. Delete empty columns and words like 'Optional', you have to only have the definitions in the syntax
I mean clean up things like this:

<field>
<label></label>
<name>related_to</name>
<table></table> {optional}
<columnname></columnname> {optional}
</field>

or the comments like {optional}.
I would recommend you start with fewer columns and keep adding and see if it is ok. A normal column would be defined like this

<field>
<label>Quote No</label>
<name>quote_no</name>
</field>

label - what you want to appear in column name
name - name of the field you want in.

Maybe some fields will require more than that, you may encounter those. custom fields usually works
And update your code if it's older than autumn 2020, I think the custom fields problem was solved then.