“On its face, Trump’s argument for doing this is absurd. The compliant Republican-controlled Senate has confirmed most nominees this president has put forth. Yet some of the most critical positions in the government — including the secretary and deputy secretary of the Department of Homeland Security — remain without a confirmed official in place to this day not because of Senate dawdling but because the president hasn’t gotten around to making a selection. Indeed, Trump has said that he likes having senior roles in government filled by acting officials, who may be more eager to please him. In the middle of a pandemic and with the economy in a tailspin, it is a dereliction of presidential duty to have left the government so woefully understaffed.”
Jeremy Paris, Washington Post

Moreover, “Despite Trump’s claim that he has a ‘very strong power’ to adjourn Congress, this power is actually quite limited. The Constitution provides that the president may adjourn both houses of Congress ‘to such Time as he shall think proper,’ but only ‘in Case of Disagreement between them, with Respect to the Time of Adjournment.’ Thus, the president’s power to adjourn Congress is only triggered when the two houses disagree about when to adjourn… right now the House and Senate are in agreement about when to adjourn — they plan to formally adjourn on January 3, 2021…

“All of that said, if McConnell were determined to engineer a situation where Trump could make recess appointments, he could most likely do so… Let’s suppose, for the sake of argument, that Trump succeeds in adjourning the Senate. Then what? The most likely answer is that Trump would have to keep Congress out of session for a decent amount of time… Democratic political operatives couldn’t dream of a more damaging story to tell about Trump during a presidential election year. The president is threatening to delay stimulus legislation, relief for many people who are unemployed, and potentially funding for necessary public health measures, over a petty dispute about a few political job vacancies.”
Ian Millhiser, Vox

“The Senate is holding formal sessions every few days. Those formal sessions mean that the Senate is not in recess and that President Trump cannot use the recess-appointment power to unilaterally make appointments. This, by the way, is exactly what the Senate did during President Barack Obama’s term to prevent him from making his own recess appointments. And in 2014, the Supreme Court upheld the Senate’s power to do that…

“All this talk of adjournments and recesses may sound technical. But many important principles of constitutional law are embodied in constitutional fine print. Most obviously, a president cannot just make Congress disappear when he wishes—in order to end an oversight investigation, for instance, or to prevent Congress from voting against a war he would like to wage. As for the question of staffing the government, the Supreme Court explained in its 2014 decision that the primary method prescribed by the Constitution for appointing officers of the United States—including the attorney general, Supreme Court justices, and more than 1,000 other varied jobs—is presidential nomination plus Senate confirmation… The president generally can’t just cut Congress out of the picture.”
Neal K. Katyal and Thomas P. Schmidt, The Atlantic