This API is reliable and breaking changes are unlikely.
backendApi.expandLeft(qRow, qCol, qAll)
Expands the left dimensions of a pivot table. Only works for hypercubes with qMode = P which are not always fully expanded.
If set to true, qRow and qCol are ignored and all cells are collapsed.
A promise of a Qlik associative engine reply.
this.backendApi.expandLeft( 0, 0, true );