Technically in DocuSign, Users are closed and never removed or deleted. Closing a User account leaves the envelopes where they are but disallows that User to access or login to the account. The envelopes for that closed User can be "shared" or perhaps a better option is to "Transfer" the ownership of those envelopes to another DocuSign User. Here is a DocuSign article regarding the transfer of envelopes....

https://support.docusign.com/en/guides/ndse-admin-guide-transfer-envelopes-templates

How do I close a user?

You must be a DocuSign Admin on the Account to start and here are the instructions.....

https://support.docusign.com/s/document-item?language=en_US&bundleId=pik1583277475390&topicId=uwb1583277426266.html&_LANG=enus

Hello I will be leaving the district and I have added my replacement. However, I do not have a close option to remove myself under users.

You cannot "close" your own User, another DocuSign Admin would need to close your user. I believe the reason would be that closing the User would basically remove your access from the DocuSign Account and if you were the only Admin and you make a mistake "closing" your User then you would need to go through DocuSign Support to regain access.

What would you recommend in regards to closing an admin user who has created custom document fields? The user was a contractor who did our DocuSign to Salesforce integration but technically should not have access to our DocuSign account any longer as the work has been completed. Thanks!

Here is what I would suggest. The Templates that have these Custom Fields should be fine if the Admin Contractor user is removed because the field is embedded into the Template. I would then have another Admin create an envelope or Template, add these custom document fields into the envelope/template and then save each one to a new Custom Field. Share the new Custom Fields as needed, then once all Custom Fields have been copied, disable the Admin contractor.

I have a User who is going on a leave of absence for a few months. If I close off their User account, can I reopen it on their return with everything still in place?