Each forged ballot is a crime. It shouldn’t take an outcome-switching level of them to be already known, now, for any trial to begin.
Trump’s team just needs to show enough probable cause to earn the right for all the ballots to inspected, to see how deep the illegal ballots already found run into the whole.
Probable cause is for the defense, in this case Biden, or no?
The problem is no court's going to order some big election disrupting inspection absent significant, specific evidence of a widespread problem.
The campaigns and parties have had a year or more to examine and sometimes litigate the election process in each state. Every state allows observers from both sides, and when there's a problem like in Philly where the observation station was too far away they can go to court and get it changed.
Given this the burden on either campaign to have the courts intervene is pretty high.