Option A — Don’t change the library: add a helper that cycles to a target

Use spa.get_pumps() to refresh state, then toggle the required number of steps.

from smarttub.api import SpaPump

PUMP_CYCLE = [SpaPump.PumpState.OFF, SpaPump.PumpState.LOW, SpaPump.PumpState.HIGH]

async def set_pump_state(spa, pump_id: str, target: SpaPump.PumpState) -> SpaPump:
    # 1) read current
    pumps = await spa.get_pumps()
    pump = next(p for p in pumps if p.id == pump_id)

    # 2) compute forward steps in the OFF->LOW->HIGH cycle
    cur_i = PUMP_CYCLE.index(pump.state)
    tgt_i = PUMP_CYCLE.index(target)
    steps = (tgt_i - cur_i) % len(PUMP_CYCLE)

    # 3) toggle steps times, refreshing state each time
    for _ in range(steps):
        await pump.toggle()          # sends POST pumps/{id}/toggle and waits for a change
        pumps = await spa.get_pumps()
        pump = next(p for p in pumps if p.id == pump_id)

    return pump


That gives you deterministic control of OFF, LOW, and HIGH, even though the underlying API is “toggle only”.

Option B — Improve python-smarttub: add set_state() (and make toggle() update self.state)

If you want this to feel “first-class”, you can patch the library so SpaPump has a set_state() method.

Conceptually:

class SpaPump:
    async def toggle(self):
        current_state = self.state
        await self.spa.request("POST", f"pumps/{self.id}/toggle")
        state = await self.spa._wait_for_state_change(
            lambda s: any(p.state != current_state for p in s.pumps if p.id == self.id),
            get_status_method=self.spa.get_status_full,
        )
        # update our state from the returned fullStatus
        self.state = next(p.state for p in state.pumps if p.id == self.id)
        return self.state

    async def set_state(self, target_state):
        order = [self.PumpState.OFF, self.PumpState.LOW, self.PumpState.HIGH]
        steps = (order.index(target_state) - order.index(self.state)) % len(order)
        for _ in range(steps):
            await self.toggle()


Then Home Assistant (or your own UI) can expose a 3-option Select instead of a Switch:

OFF

LOW

HIGH