When configuring SCIM instance, I do not see DN as part of available attributes. I am looking to map DN value.
Unfortunately, what you want to see is not there by product design.
Under the covers, the SCIM instance queries the associated DSA's all schema files that are sourced in and applies two set of filters.
First filter gets list of all 'structural' objectClasses that are known to the DSA.
Second filter queries those returned objectClasses list to narrow it down to the ones that have "name form" entry.
This final list is displayed as an available objectClasses (and all those attributes present in them as part of must-contain list).
As the 'DN' doesn't belong to any objectClasses (defined as an attribute name itself in x500.dxc schema file), it is not visible to SCIM instance hence you are not able to see it.