Neither the Constitution, nor the War Powers Act allows the president to remain in office after his term expires. In fact there is no provision for a president to remain in office after the end of his term, neither war, national emergency or civil uprising.
Using force to remain in office would probably result in impeachment or use of the 25 amendment to remove the president . In any democratic republic, the chance of a president seizing control is aways a possibility.
I don't think Trump would go this far to remain in power. However, his behavior leading up to Jan 6, his obsession with the loyalty of his staff, and respect for dictators, makes one wonder.