To ensure the heating will remain operable with or without an internet connection the schedule is necessary for operation. If you would like it to be off/setback all day and only turn on 'on demand' then this may be possible by setting a simple schedule to have a setback temperature at a lower temperature and a single on temperature with 1C difference.
An example of this could be to have the heating at 10C setback, with a 12AM-1AM target of 11C.
When not in operation, the heating would only come on if the temperature dropped below 11C. If you were to set a higher temperature on demand throughout your day, then this would stay on until midnight when the 11C schedule change would occur.
OFF TEMP (Setback Temp) :
The Off temperature isn’t the temperature at which the heating will be switched off. The off temperature is used to be a target for the “off” periods in your schedule. Ordinarily, you wouldn’t want your heating to be completely off, but to have a lower target temperature. This will result in the property not getting overly cold, and when heating is needed, it won’t need to heat up for so long. You can set your setback/off temperature to be very low, such as 1C or 2C if you’d like so the heating does not come on, but it must be lower than the “on” temperature.
If wanting to have to control the system on demand only (ON/OFF), We would suggest creating a "dummy" schedule in it which will have a setback temperature of something low, with an "on" block for an hour or so which is 2C higher overnight. This would allow you to have "on demand" heating and if you were to forget to turn the heating off, the scheduled block overnight would essentially do it for you.
Even if a schedule is not set in the app, there is still a schedule (i.e. to be on all day, every day) therefore it is not "schedule-less". So if you had set the device to be "On" with a manual update, the schedule for the next day would kick in and take over on the next day.
The Electric Switch, and all heating products store their schedule internally. They have a schedule for each day of the week and will switch based on this schedule. The system will detect when the next change point is and switch to the new target when that time comes. The 6AM-6AM schedule was designed to match most peoples "days", and is ingrained into the peripheral devices so is unable to be changed.