Yes it can be done as each certificate that is uploaded into the system will generate an unique Alias Name (certalias___8648725) like this.
Please refer the below link for more details:
I do follow the same instructions but the issue is my old cert got overridden once new cert uploaded.
I hope it may be due to cert generated from same company (OKTA) but it has diff SP ID.
I can see if OKTA can generate something different in configuration so that diff alias will be generated