Do you want to add "Title" to the same list of radio button values already in place?
If so, you can add:
"¶" & Title
To the end of the calcualtion for k_Similars_MultiKey
And change K_Simalars to be:
g_Similar_By = "Name";
g_Similar_By = "Company";
g_Similar_By = "City";
g_Similar_By = "Title";
Then open Manage | Value lists and edit the value list for Similarity Criteria to include "Title". You will also need to resize the radio button field to be wide enough to display the added radio button value.
PS. If I had created this starter solution, I would have used this expression for k_Similars_Multikey:
List ( k_Similar_NameMultiKey ; Company ; City1 ; Title )