Logging trigger

Is it possible to define any button on the car to start or stop logging by the driver?

That depends. Different firmware may make this easier, but for the MoTeC GP packages:

Logging can be configured to start above a certain RPM or Throttle Position. This sets the "Logging Request" channel, and is used for the Level 1 Logging.

If you have Level 2 Logging, you can configure another logged data set that is enabled when any Off/On channel is active. If so ...

Can the "any" button on the car be configured in M1 Tune as a "Driver Switch' that has a switched Off/On State (not just momentary)? Then you can use this as the activate condition channel for the other data sets.

I will tell you from experience, you want "automatic" logging, so nothing has to be done to log the data. Switches sound like a good idea, and are often forgotten just when it's really needed.

Set and forget is the best option for logging, the time that you forget to set the logging is typically the time that you need it most.

For a car on street driving, most of time we don’t need the log. Only at some certain situations, we may need the customer to make a log at that moment.

But you can have the logging continuously write over in a loop, that way you always have the last few hours of the engine running (depending on your log set - I have about 65 minutes of logging on my M150), which means if someone ever runs into an issue, the logging is always there.

Some cars are for daily driving, that means most of log are worthless to me.

My M150 logs more than 18 hours worth of diagnostic logging. That's just engine running time, so it's a lot of data. It's often useful to see the pattern or driving conditions, but hopefully your original question has been answered.