Merge into one file in the main interface can merge all the loaded files to one file.
Or you can merge several random files by below steps:
1) Click one of the files in the Leawo file list;
2) Keep button “Ctrl” pressed and click the one you want to add;
3) Then right click the blue/highlighted Zone;
4) Click Merge, you will get Merge1;
5) Check Merge1 to convert.