With the advent of the COVID pandemic, sometimes games are cancelled last-minute before the start of a slate. If you need to quickly remove all players from a cancelled game here is the fastest way to do it:
1) Click Set Pro Options and create a template. The template will contain a line that starts with "Inc Teams:".
2) Now, just delete the teams in this list that aren't playing and save the template. For example, let's say the NYM/StL game has been cancelled then we would just delete "NYM" and "STL":
3) Then from the bottom of the Set Pro Options pop-up click "Choose File" to select your edited Pro Options template, and then click "Use this file":
4) Now the players in the Available Players table should change. Here is an before and after image: