When you start scidCommunity from a shell or console, there are command-line options you can specify. scidCommunity-format databases (with or without a file suffix such as ".si3") and PGN files to be opened can be given, for example:
There are also optional arguments to control which files scidCommunity should search for and use when it starts. You can turn off the use of tablebases with the -xtb (or -xt) option, avoid loading the ECO openings classification file with -xeco or -xe, and avoid loading the spelling file with -xspell or -xs. Also, the option -fast or -f does all three, so scid -f is equivalent to scid -xeco -xspell -xtb.