Mr Trump is free to appt anyone he wishes when Congreff is in recess. Hell, he could even appoint Extra Goat Roper without issue.
Ignoramus. Here's a quick summary from Wikipedia concerning the Vacancy Act of 1998. Provisions The law designates three classes of people who may serve as acting officials: By default, "the first assistant to the office" becomes the acting officer. The President may direct a person currently serving in a different Senate-confirmed position to serve as acting officer. The President can select a senior "officer or employee" of the same executive agency who is equivalent to a GS-15 or above on the federal pay scale, if that employee served in that agency for at least 90 days during the year preceding the vacancy.
https://thehill.com/policy/national-security/432477-whitaker-out-at-justice-department Whitaker out at Justice Department Former acting Attorney General Matthew Whitaker has left the Department of Justice. A Justice Department spokesman told The Hill that Whitaker’s last day was Saturday but did not expand on the circumstances surrounding his departure or his plans after leaving. It is unclear where Whitaker might go, including whether he might seek another role in the Trump administration. Whitaker served as the chief of staff for former Attorney General Jeff Sessions until November, when President Trump tapped him to lead the department temporarily following Sessions’s ouster. Sessions resigned at Trump’s request the day after the November midterm elections, after enduring months of criticism from the president over his decision to recuse himself from special counsel Robert Mueller’s Russia investigation. Whitaker’s departure comes less than three weeks after William Barr was confirmed as Trump’s next attorney general. Barr was widely expected to bring new blood to top leadership roles in the department, raising questions about Whitaker’s tenure.