A party of ten arrives and takes two tables. The floor solves this in seconds; most systems make somebody choose which table "owns" the bill and then work around that choice all evening.
Because the bill belongs to a party rather than to a table, joining is an attachment: a second table joins the party, and both are freed when the party closes. Nothing is copied, nothing is re-keyed, and the folio never changes identity.
Removing a table from a multi-table party is the same operation in reverse, with one guard — the last active table cannot be dropped, because a party with no table is not a smaller party, it is a party nobody can find. Close it instead.
Merging two parties that were opened separately is non-destructive: the source becomes a child of the target and the audit trail of both survives.