If you check the keybinding for { in the keybindings dialog (or use the list-keydefs command), you'll see it's bound to a function called c_begin for "c" languages.
Type this on the slick command line
fp c_begin
and you'll get to the c_begin function. All the hard work is done by the call to c_expand_begin (a 400 line function), after which there's beautify while typing stuff.
If you type int abc{ - no space before the brace, slick produces {}.
If you want you could bind a key like Ctrl-shift-{ to the macro below - add it to your vusrmacs.e file and load it with the load module command in the macro menu.
For CUA emulation you'll see that shift+enter inserts a new line without doing any syntax expansion and shift+space inserts a space without doing syntax expansion.
_command void my_c_begin() name_info(','VSARG2_MULTI_CURSOR|VSARG2_REQUIRES_EDITORCTL|VSARG2_CMDLINE)
{
_insert_text("{ }");
cursor_left(2);
}