Stanislav Sendek 

Stanislav Sendek said:

When I added a source file for translation, the target file appeared in the "German (Austria)" target folder and not in "German (Germany)" target folder.  How can I decide on the source file to be assigned in the right target group that I choose?

They might be both "German", but in your project they are considered different languages.  So if you create a project with both variants on purpose you would have to translate the files in both languages to get a target file for each one.

Stanislav Sendek said:

How can I decide on the source file to be assigned in the right target group that I choose?

When you open the source it will be open in the language you selected in your screenshot.  You seem to have German (Austrian) selected so the language pair you're working in with this multilingual project is Slovak (Slovakia) into German (Austrian).

Stanislav Sendek said:

TMs are not updated according to which target folder is affected upon translation. This setting is missing. All translations go into the same TMs after translation.

Missing because you have not created a TM for the missing target language.

Stanislav Sendek said:

Any suggestions for repairing these settings?

I think you should clarify if you did this on purpose or if you just found yourself with this predicament because you don't understand how Studio works in this regard?  If we don't know this we may give you advice that just creates unnecessary work for you in the future.