I've read numerous times, that you cannot delete single dives from the OSTC's logbook (please let me know if this changed meanwhile ) but I am wondering, whether one can add single dives. Maybe with subsurface?
The other week I made a dive without my OSTC which I would love to manually add now.. Is that possible?
Sorry, neither - nor... The way the logbook and dive profile data are stored does not allow to insert or remove single dives.
Technically, the storage is organised as a ring buffer: Dives will be stored until the end of the dive data memory is reached. Then memory access wraps around to the beginning again and the data of the first dive are deleted to make room for the current dive. As soon as the memory that became free by doing so is used up again, the next dive's data will be deleted, and so on. This way the storage is optimised to hold the data of a certain overall dive time, independent of the duration of the individual dives. When one would like to insert a dive, everything would need to be moved around in memory (EEPROM) to make space where there is none. On deleting a dive, a gap would be created, but that could not be handled by the existing data structures and access routines. So there is also no plan to add such a features, as it would require large portions of the logging and retrieval code to be rewritten.