I know Texans like to believe that, but they are as misguided on this topic as they are on what true barbecue is.
https://www.ksat.com/news/local/2020/11/05/can-texas-secede-from-the-us/
https://texassecede.com/faq.php
These are just two of a multitude of articles about the myth of Texas’ right of secession being somehow different than any other state.
“What a state (or states) can do, however, is begin the process of seeking a mutually agreed upon parting of the ways, and that process clearly exists, set forth by the U.S. Supreme Court in its 1868 ruling in Texas v. White. That ruling concluded that a state (or states) could secede by gaining approval of both houses of Congress and then obtaining ratification by three fourths of the nation's legislatures. In other words, it's a tough task.”
https://blogs.findlaw.com/law_and_life/2020/10/could-states-really-secede-from-the-union.html
How does the secession actually happen?
State referendum...vote of the legislature...governor exec order...or ??
It really is pointless to look at law with this, no way any state would be given permission to leave. If the time comes, you just prep for consequences and leave.