After playing with exporting set of projects, I understood that small merge utility will save my time.
https://github.com/Volccc/shpmerge
I spent only couple of hours, so it is lack of error handling, but it works with RM2 export.
It simply combines all shape files into 3: merged_Isobaths, merged_Major Contours, merged_Minor Contours.
Very useful for me (import in GME), maybe somebody else will find it useful.