Hello,
you are going in the right direction. For the ??? part you need to specify transaction NetObject id. That is basically transaction id that you can get from a select query prefixed by T: string. So for example for transaction with id 1 the first parameter should be "T:1". Invoking the unmanage verb can be done only for one transaction at time, so you will probably need to preselect transaction ids for all transactions that you want to unmanage and then in the loop invoke the unmanage verb.
To explain the parameters of the "Unmanage" verb, the first parameter is NetObject id of the transaction that you want to unmanage, the second one is the time from when the transaction should be unmanaged (it should be in UTC). The third parameter is time when the transaction should be remanaged (once again should be in UTC). Last parameter specified whether the remanage time is relative or not (if you pass true in this parameter and the remanage time will be set to 2 AM the transaction will be unmanaged only for two hours).
If you need to remanage any node before the scheduled remanage time you can invoke "Remanage" verb to do that. Syntax should be following (just replace the NetObject id with the correct one):
$swis->Invoke("Orion.SEUM.Transactions", "Remanage", ["T:1"]);
Let me know if you have any questions.
Lukas