@Katherine-Curran
Find: (?-s)^(.+?):(.+)\R\1:(.+)
Replace: ${1}:${2}${3}
Wrap around: ticked
Search mode: Regular expression
Press Replace All repeatedly until the status bar of the Replace window indicates 0 replacements made
Example:
John Doe: Hello.
John Doe: How are you today?
John Doe: I hope that you are well.
Bob Doe: Hello.
Bob Doe: How are you today?
Bob Doe: I hope that you are well.
John Doe: Hello.
John Doe: How are you today?
John Doe: I hope that you are well.
After the first Replace All press:
John Doe: Hello. How are you today?
John Doe: I hope that you are well.
Bob Doe: Hello. How are you today?
Bob Doe: I hope that you are well.
John Doe: Hello. How are you today?
John Doe: I hope that you are well.
Status bar indicates 3 replacements made.
After the second Replace All press:
John Doe: Hello. How are you today? I hope that you are well.
Bob Doe: Hello. How are you today? I hope that you are well.
John Doe: Hello. How are you today? I hope that you are well.
Status bar indicates 3 replacements made.
After the third Replace All press:
John Doe: Hello. How are you today? I hope that you are well.
Bob Doe: Hello. How are you today? I hope that you are well.
John Doe: Hello. How are you today? I hope that you are well.
Status bar indicates 0 replacements made. (Data transform was actually complete with the previous press, but that can only be determined via visual inspection).