Is there a better way (aka When will I see you again)

Setting an absolute value manually at any given time may not achieve the desired effect because it depends what the present value being generated by the automation is doing at that time and what the room temperature actually is. Only if you have flat lines for both the occupied and unoccupied profiles and no external temperature compensation can you be sure what the offset would be relative to such profiles at any time when you request a manual change to a particular value (and even then that would be relative to either the occupied or unoccupied profile if these are different and the room is occupied or not...). For example if you are occupying the room and the normal occupied set point profile is saying 22C then setting a temporary change to 21.5 would result in a -0.5 offset rather than an increase. Furthermore, If the room temperature was actually 24C at the time then what you would then get is effectively a request to turn down the temperature by 2.5C...

I think there can be better ways to achieve the desired effect. For example you can use something like 'Heating Increase Temperature'. This is quite different in concept to just increasing the set point because what it actually means is that Cortex will check the current room temperature and add 0.5C to this and then use the resulting value as the temporary new set point. That way it doesn't really matter what the present profile value is or the actual room temperature, you will always get the heating coming on. Note that temporary changes such as these would usually be reverted back to the normal profile upon the next change in the profile shape (and I believe also at midnight). So something you might have to think about in the overall profile schemes you use. There is a control to make temporary changes persist but again you might need to consider whether this is better or not than the automated removal scheme depending on your particular circumstances. If you want to manually or by some other method remove temporary offsets you can use the 'Heating Normal Setting' connection.

If you just want to use a single button control to override the heating automation decision at any given time, you can use the 'Force Heating Change State' connection. Essentially if the heating was not on at the time of triggering this connection then Cortex will contrive what it considers might be a suitable way to get heating on and vice versa if the heating was already on. This type of control might be better suited for some types of user interface but is not the same as the above. For more detail you can read the Help sections in Cortex (easiest from the HVAC connections menu help link). This should help you to better understand how Cortex decides on what to do under different circumstances given that a number of factors can affect the set point decision at any given time.