What flow temperatures are you currently running?

How many meters is the pipe in the bathroom? You can increase the flow at the Taco and the valve, for that you need a square key. And because of the whisper mode, you have also reduced the pump power.. therefore your hot water finds the easiest way.

Taccosetter for the bathroom is already fully open, I have to test the whisper mode, I thought it only reduces the compressor power

And the valve fully open as well? The actuator is usually located there.

Yes, the valves are open... turning whisper mode on or off has no effect on the pump performance or flow rate in the underfloor heating circuit.

what does your hydraulics look like?

the design is such that the specification for 35°C supply temperature on NAT is already being met.
unfortunately, this also means that in most cases "only" 20°C room temperature is taken as the target value.
the bathroom is therefore undervalued for a temperature of 22-24°C. you won't achieve that even if you increase the flow rate.
the only solution here is to increase the supply temperature...

And the valve fully open as well? The actuator is usually located on it.

I have something similar under the actuator, but not a hexagon, rather the "radiator square" for the thing under the pin for the actuator. If I unscrew it, will the flow then increase, or is it simply an adjustment of the actuator’s travel stop?

With my valve, I turned the one on the return line, but didn’t notice any change in flow.

Put differently, what do you have to turn to remove the restriction?

what does your hydraulics look like? it is such that the design for 35°C flow temperature on NAT is already being met. However, this unfortunately also means that in most cases "only" 20°C room temperature is taken as the target value here. The bathroom is therefore under-covered for a temperature of 22-24°C. You won't achieve this even if you increase the flow rate. The only solution here is to increase the flow temperature...

Yes, that may be true that I can only achieve the temperature increase in the bathroom with higher flow temperatures. Then the question is whether I raise the flow temperature to achieve, for example, 22°C in the bathroom (which would then apply to all heating circuits) or if I hang up a purely electric towel radiator and have it heat by timer or on demand... Madame wants something like that anyway to hang towels and dry them faster...