Katharina Ledermann-Tappeiner 

If the projects are prepared by yourself and the merging is a result of segmentation on a colon or unknown abbreviation, modify your TM settings to not segment there.

In any other case or if you are merging independent sentences into one (segmentation is correct in this case), you can lower the minimum match value to something like 50% in order to force Studio to show you matches which may contain such merged sentences. You can also (if not yet activated) activate the automatic concordance search for segments.

Another idea for your own projects would be changing the segmentation to paragraph based.

Katharina Ledermann-Tappeiner 

The first step might be to activate automatic concordance search, but keep the minimum TM search value high. Automatic concordance seach only kicks in when there are no TM search results.

Daniel Hug 

In her case there will be bad matches or no matches with a high match value. I work with 50% and I get quite good results. But I think it is also a question of habits. With the Workbench I used to work with 30%...

I think the best option will be checking the settings and changing them one by one in order to estimate the best result. As with all settings in Trados Studio, there is no set of settings suitable for every possible case. The trick is to be aware of all the possibilities given and adapt the settings to the art of work you have to perform. In this terms I do not know any other tool allowing so many possibilities and giving you the power to work your way as Studio does.

Thank you for these suggestions, I will definitely try them!