SMET_APPEND vs SMET_OVERWRITE
With a recent change, it is not possible to set SMET_OVERWRITE and SMET_APPEND to true. However, this breaks current setups, where SMET_OVERWRITE was true by default, and one could set SMET_APPEND = TRUE to trigger append mode.
Now, those two keys are mutually exclusive, which makes sense, but is also a bit clumsy. Changing from overwriting to appending smet, requires now 2 keys to be specified and set accordingly.
I think a better solution would be: SMET_MODE = OVERWRITE / APPEND, and make the two keys SMET_OVERWRITE and SMET_APPEND behave like before, but mark them as deprecated. I.e., show a warning that those keys need to be changed because they are deprecated and marked for removal at some point in the future.