Rottary encoder and STM32 - multi speed

I have a variable <0-10.000>
I want to use a rotary encoder 30 pulse per revolution to set it up.
Given the range of the variable, I want the variable to be a variable at least three different steps depending on the speed.
For example for low speed 1 , for midle speed 5 and high speed 50.
I think this is a classic requirement that many people have addressed in advance.

Give you an example, a library that can do it?
If not At least at what speeds of rotation to change ranges so that such a change would be fiziologically natural for him who is spinning?
With STM 32, the timer can be set to Encoder mode, but I have to solve the rotational speed measurements.
The first option is to use a second counter to measure the rotation speed. for exampe as

slave counter

Does it seem a bit like a waste of hw resources, some other smart idea?

In general Encoders are not read in polling strategy, it is used I/O interrupts, and depending of the rate it is needed a dedicated hardware for that, appart from the microcontroller, otherwise it will lock other tasks. Anyway, the question as posed is a bit unclear, essencially you should provide the following information:

• Encoder type, incremental or absolute?
• Encoder resolution in pulses.
• Maximum rotation speed of device to be measured
• Is there motor reduction?

Encoder is incremental with 30 or 60 pulse per revolution.
It is actually a "potentiometer" with knob for setting the time 0- 10.000 ms
yes, the knob rotates the operator, when it needs to set the duration of an operation.

I'm not sure if it is a good idea to measure rotation speed from knob; handling may vary a lot from one person to another, so the criteria you defined above may not work. Long time ago I did the ISR handler for a Knob pot used as the browser of a wide screen menu, very simple. As you know, there is a well defined pattern when it turns in CW or CCW direction, and with switch...case statements you can do it, either incrementing or decrementing a counter as long the next patern is one of another; in the case of a patterns not belonging to the current state, simply ignore it and restart the machine state.