Picking and Choosing What Transactions Go on Invoices

Hi there! We would like to be able to pick and choose what transactions go on invoices to members. 

We invoice league captains for court fees for their team's matches for the entire season. However, we have captains that captain multiple teams in one season. We would like to select specific courts fees for each team that the captain is on and provide separate invoices that they have been requesting. 

We have some students where work or a school program can pay for some classes but not all the classes that they take. We would like to give them a specific invoice for the classes that their work or school can pay for. 

We are a popular choice for events, so many companies will book multiple events at one time but will need separate invoices. 

We would like to be able to choose what transactions go on invoices and have multiple uses for this functionality.