One of the tactics the Demo-Left is using to thwart the President is to stop the appointment of Federal prosecutors. They are using the blue slip process whereby both Senators from the home state of the appointee have to concur. This was rarely used in times past, and when it was - such as the case of
Ronnie White, who was blackballed (pardon the expression) by then Missouri Senator John Ashcroft for good cause (among other things White called a plaintiff a "mother effer" in a legal opinion) the Democrats have gone bananas and demander the blue slip process be rejected. But now they are using it as a weapon to stop the MAGA movement.
And there is another issue; they are using judges to disqualify presidential appointees as interim prosecutors. This has led to the dismissal of multiple charges against crooked folks like Letitia James; it's purely a legal maneuver and has gotten James and James Comey and others off scott-free despite obvious guilt.
This article analyzes the problem; it's putting the judiciary in a position of making executive decisions in a flagrant violation of separation of powers. Courts are not supposed to make or enforce the law - they are supposed to apply it.
The article deals with the complicated matter and says we've had this for some time and the author believes the Founders wanted to let the courts have this power for inferior officials (I think he's wrong, and base that on my reading of the Federalist Papers but he looks at this more as a lawyer than do I).
So what can Trump do? One question is can the President simply put a new guy in the interim before the 120 time frame expires? That has never been fully dealt with. There is no reason if the President has put the name of his chosen appointee before Congress, which is failing to do it's job, that the courts should then usurp his authority and appoint their own choice. If the letter of the law only allows 120 days then the President should be able to appoint a new guy, maybe rotate them. But it's not the courts that should have any right to decide; these appointments are supposed to be political matrers, and the People choose the President. The courts are lifetime appointments and so you get the very thing we are seeing - self-serving scoundrels and partisan hacks who twist the political landscape for decades because of lifetime tenure. The anti-federalists warned about this and they were right. Hamilton argued the courts could simply be ignored. He was wrong.
I suspect this is but another issue that will wind up at the Supreme Court. How can the President represent the people who voted him into office if Congress simply shirks it's responsibility and then courts simply overrule him on his selection to staff his own branch of government? In a sane world Congress would rein in these courts but this is not a sane world and Congress has no real interest in anything that doesn't cement their own power and privilege.