Right after saving
The confirmation screen of Log service has Undo. The entry disappears, the intervals stand as they did before. That also applies to services you ticked off under In Focus or logged through the bike assistant.
Editing
Editing happens on the Workshop page under Service history: tap the pencil on the entry. That only works for the newest service of a component; older entries and swaps stay fixed. Under Edit service you change date, work done, note and cost. On the bike page and in the service book you only see the details. The service book notes on the entry when it was last edited.
Voiding
If an entry is wrong, choose Reverse in the edit dialog. Velopit asks once. The entry is not deleted but marked Voided and hidden from lists and the service book. In the workshop's service history the eye icon Show voided entries brings it back, struck through. That way it stays traceable for you what happened.
If you change the date while editing, Save turns into Reverse & correct: the old entry is voided and a new one with the corrected details is created. Both are linked, the service book shows Corrected.
Why there is no delete
A service book from which entries vanish without a trace is worth nothing. That is why there is voiding instead of deleting. The immediate undo does not delete either: the entry disappears from the lists and stays visible with the voided entries in the workshop's service history.