Hi @anjali s welcome to the Atlassian community. Based on your query, I understand you are referring to Jira Issue security schemes!
Please be informed, there is no limit to the number of security levels you can add to a 'Jira issue security scheme'. When creating/editing an issue you can specify a level of security for the issue. This ensures only users who are assigned to this security level may view the issue.
To add a new security level to a Jira issue security scheme, follow these:
Go to Settings > Issues > Issue security schemes.
Click the name of the security scheme that you want to edit.
OR
Click Add issue security scheme.
Enter a name and description for the security level.
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