Set up the range that you want to export and then export it with an appropriate file type and name. To use in other projects, I usually use Magix mxv format. Make sure to check the box "Export selected range only." Then import the mxv into the other project(s).
Open your project and select the clip or object you want to copy use key Ctrl C to copy in memory, begin or open another project and select the track you need to paste using Ctrl V keys on your keyboard.