If it is for Articles - https://help.salesforce.com/articleView?id=sf.knowledge_create_anchors.htm&type=5.
From Custom Aura Component - https://developer.salesforce.com/docs/atlas.en-us.api_console.meta/api_console/sforce_api_console_lightning_openSubtab.htm
Example for Aura Component - https://www.infallibletechie.com/2020/06/opensubtab-for-lightning-experience-in.html
For Flow, vote for this idea - https://trailblazer.salesforce.com/ideaView?id=0873A000000LrXrQAK
