Does that mean I can pass the parameter directly to pihole-FTL process?
I guess I missed that the long option is how we set the config in a file, sorry 
CONFIG FILE
At startup, dnsmasq reads /etc/dnsmasq.conf, if it exists. (On FreeBSD, the file is /usr/local/etc/dnsmasq.conf ) (but see the --conf-file and --conf-dir options.) The format of this file consists of one option per line, exactly as the long options detailed in the OPTIONS section but without the leading "--". Lines starting with # are comments and ignored. For options which may only be specified once, the configuration file overrides the command line. Quoting is allowed in a config file: between " quotes the special meanings of ,:. and # are removed and the following escapes are allowed: \ " \t \e \b \r and \n. The later corresponding to tab, escape, backspace, return and newline.