awk -F= '/\$\{B_D\}\/user_projects\/@B_D_N@/{$0=$1"="v1}
          /t3:\/\/@U_S@:@A_S_P@/            {$0=$1"="v2}
          /@U_H@\/keys\/@B_D_N@\/@K_S_D@/   {$0=$1"="v3}

          ## repeat the same thing for all of your tokens, using their actual names, and escape special chars:     - $ / + * ? . etc 

                                  1' v1="$v1" v2="$v2" v3="$v3" "$file" > "$path"/"$file"

# ./replace.sh

enter 1st value:
"t3://U_S_Tag_Value:A_S_P_Tag_Value"
enter 2nd value:
"other variable goes here"
enter 3rd value:
"000 000 000"
enter full path to temp dir:
/home/user/test

------

$ ll test
-rw-r--r--   1 user       sys            557 Oct 28 19:37 file_1ABC
-rw-r--r--   1 user       sys            557 Oct 28 19:37 file_2ABC
-rw-r--r--   1 user       sys            557 Oct 28 19:37 file_3ABC
-rw-r--r--   1 user       sys            557 Oct 28 19:37 file_4ABC


$ cat test/file_2ABC

##################################
#Header of script, place values in variable names#
##################################
S_N="@A_S_N@"
B_D="@B_I_D@"
D_B="t3://u_s_Tag_Value:a_s_p_Tag_Value"
D_D="${D_B}/@D_N@"
S_U="other variable goes here"
A_U="t3://@A_U_S@:@A_S_P@"
K_D="000 000 000"
VAR_MAN_NAME="@MAN_NAME@"
VAR_PORT_NUM="@PORT_NUM@"
VAR_TEST_NUM="@TEST_NUM@"
###################################
#---------------Script Logic---------------------#
###################################
.
.
.
This section uses all the variable names, and doesn't use any flags