Hi,
As Robert already said, only script units which are a plain script files can be merged (with all merging risks that exist for merging source code). All other components of TestComplete project are near to impossible to merge either automatically or manually.
You have only two options: either stick to Robert's advice or to force all team members to announce their changes immediately after they made them and all other team members must reload their projects immediately after they receive such announcement. (Something tells me that the choice is obvious...)