Load an element from DBM to MTE. Make some changes in MTE.

When you are finished save the element or project back to the DBM.

Back in the DBM click on "Copy data" at the right side. A new window opens.

Select all the metadata you want to copy and then click "Save" and "OK". 

Now the selected metadata are copied to the new file.

You can copy the metadata from all recently in MTE opened files.