It is because default namevalueseparator is equal sign (=) in TStrings (or TStringlist?). If you run following code,
StrLst := TStringList.Create;
StrList.Values['aname'] := 'AValue';
Showmessage(StrList.Text);
This will show
aname=AValue
Internally Name-value pairs are stored as name=value.
I do not understand why two equal signs are added to the value column, but you can change the NameValueSeparator character to other one which will not be used.
So run following sentence before you
ValueListEditor1.Strings.NameValueSeparator := '\';
And then equal signs will be entered to the key colume in ValueListEditor.