Is there a way to specify in the slimcoin.conf file the number of cores, so mining will be enabled immediately? I tried generate=4 but it doesn't seem to work.
Good guess but Slimcoin's documentation is a bit erratic here'n'there and this one's an undocumented command-line option:
https://github.com/slimcoin-project/Slimcoin/blob/slimcoin/src/main.cpp#L5451nLimitProcessors = GetArg("-genproclimit", -1);
so
-genproclimit=4 and
-gen=1 it is. Could try setting it in the config file, see if that works.
Cheers
Graham