>もともとあったものと新規に作成したり変更したものとは、明確に
>区別できるようにして頂きたいです。

⇒失礼しました。仰る通りです…
　 末尾に*等付けると後で見た時も分かり易くなりますね。

下記、snmptrapfmt.confの中身となります。
拡張Mibを見にいく設定はなさそうに見えます。

# -----------------------------------------------------------------------------
# Configuration file for snmptrapfmt-1.0
#
# Comment lines start with the character '#'
# Blank lines are ignored
#
# In order to configure the log output, use the following keywords.
# -----------------------------------------------------------------------------

# - SUBST=\a\b\
# substitute char 'a' with 'b' in variable values
# Default: \;\ \
SUBST=\#\ \

# NOTE: The OID Format has to be set in the /etc/snmp/snmp.conf.
# See SNMP.CONF(5). It is valid for all snmp programs of package SNMPD.
# You can specify it with: printNumericOids (1|yes|true|0|no|false)
#
# snmptrapfmt uses it in formats $e $*

# NODEFMT=ip | fqdn | name
# print nodenames as IP address (ip), as fully qualified domain name (fqdn)
# or in the short form (name);
# used in formats $A $R $r $*
# Default: fqdn
NODEFMT=ip

# VARFMT="format string for variables"
# specify the output of variables when using the '$*' format specifier
# in the logfile format;
# special chars recognized:
# %s ... sequence number of the variable
# %n ... the name of the variable (see OIDFMT)
# %t ... the type of the variable
# %v ... the value of the variable
# used in format $*
# Default: ";[%s] %n (%t) : %v"
#VARFMT="\n\t[%s] %n (%t) : %v"
VARFMT="#[%s] %n (%t) : %v"

# LOGFMT="format string for logfile entry"
# specify the output of the logfile entry;
# special char recognized:
# \n ... newline
# \r ... carriage return
# \t ... horizontal tab
# \\ ... backslash
# $# ... number of variables in the trap
# $* ... print all variables of the trap as specified in VARFMT
# $x ... date the trap was received (YYYYMMDD.HHMMSS)
# $r ... the implied source of the trap (agent address) (see NODEFMT)
# $R ... the true source of the trap (via transport layer) (see NODEFMT)
# $$ ... the character '$'
# $e ... the enterprise of the trap as specified in OIDFMT
# $A ... the trap agent address as specified in NODEFMT
# $G ... the trap generic number
# $S ... the trap specific number
# $T ... the trap's sysUpTime timestamp (in seconds)
# ordinary characters represent themselfes
# Default: "$x;$A;$e;$G;$S$*"
#LOGFMT="\n$$x=$x\n$$r=$r\n$$R=$R\n$$e=$e\n$$A=$A\n$$G=$G\n$$S=$S\n$$T=$T\n$$#=$#$*"
LOGFMT="$x#$A#$e#$G#$S#$T$*"

# LOGFILE="path to logfile"
# specify the pathname of the logfile; if none or the empty string "" is
# given, use the syslog() mechanism to log the traps
# Default: ""
LOGFILE="/var/log/snmptrapfmt.log"