Q: Is there any public indication that Trump and McConnell are planning on a [lame-duck Senate confirmation vote] to the Supreme Court?
It seems rather unlikely that such a plan existed since Trump nominated and the Senate confirmed Amy Barrett as an associate justice before the election.
Q: And, has [a lame-duck Senate confirmation vote] ever been done before in order to secure sufficient votes for a SCOTUS justice?
In Lame Duck Appointments? We've Had a Few, there were some mentioned — well ... a few.
The article notes that:
Lame-duck nominations were a common feature of nineteenth-century appointment politics, accounting for 16 percent of all nominations made before 1900, but there have been no lame-duck nominations in over a century. Lame-duck nominations also had a high rate of failure.
The last lame-duck appointment was Judge Howell Jackson, a former Senate Democrat. Nominated by Republican Benjamin Harrison on Feb 2, 1893, and confirmed by the Senate on Feb 18, 1893. Democrat Grover Cleveland was elected president in Nov 1892 and took office on Mar 4, 1893.
In the 1892 election, Republicans had lost both the presidency and the Senate majority. With only two months remaining, nominating a Republican would have resulted in a failed nomination. Selecting a former Democratic senator was a risk, but Judge Jackson was confirmed by voice vote. Had Harrison not nominated Judge Jackson, Cleveland may have nominated someone less acceptable to Republicans.