Sometimes we have an event registration of multiple participants from a single organisation. This creates an aggregated contribution for those participants. A while later another participant is registered but wants to be included in the invoice for the first group.
Is it possible to combine the two contributions, preferably by just adding the second, single, one to to first one?
Not sure I get all the details of your use case, but you could potentially have the additional participants sign up for free, then update the contribution with the Line Item Editor extension (https://civicrm.org/extensions/line-item-editor). Alternatively, you could set up a price set for the event registration with a price field (e.g. "Additional Amount") that's only visible to admins on the back end - if you edit the contribution, you can enter whatever amount you'd like, and it'll increase the contribution value/balance.
The following might be useful, as well: https://civicrm.org/extensions/edit-event-fee
Again, sharing all these not fully understanding your use case, but hoping one or a combo of the above would help.
