Go into your File Explorer and go to "This PC". From there go to the search bar near the top right and type (w/o the quotations) "builder.ini" From there, open it using Notepad.
If the text at the top says Recent. Replace with it Favorites and clear out any text underneath this. Just as a warning this will clear any previous tools you may have had in the Favorites bar. After doing that, save the changes you made to the notepad. You may want to open MegaMan Maker and see if the favorites were cleared, if they were. Job well done.
At this point, you may copy this text and paste it underneathe favorites. Save the file again and open up MegaMan Maker to utilize the new enemies.
While I'm sure someone has posted this before. I could not personally find any thread that had gone into detail on how to add them to your favorites so I hope this helped.used0="1.000000"