Open the file in your favorite text editor. The configuration for the favorites buttons is defined as an associative lua table inside. Locate the line with the text ["FavoriteTable"] = . This the starting point for the favorite buttons.

Here is a partial listing

...
["FavoriteTable"] =
{
[1] =
{
["ID"] = 1,
["EmoteName"] = [[torch]],
},
[2] =
{
["ID"] = 141,
["EmoteName"] = [[playdead]],
},
...

Say that you want the emotes /drink and /facepalm as the first two emote button.
[indent]
1) Then you would edit EmotesImportData.lua to.

...
["FavoriteTable"] =
{
[1] =
{
["ID"] = 9,
["EmoteName"] = [[drink]],
},
[2] =
{
["ID"] = 41,
["EmoteName"] = [[facepalm]],
},
...

2) Save the file.