This would be easier if we could see an image of a measure or two from a portion/screenshot of the song where you are trying (unsuccessfully?) to transfer lyrics from the voice to the piano staff.

If your piano part does not include the melody, then you may have to use hard spaces to put multiple lyrics on a single note, but seeing what you mean will help us be more helpful.

Try this:

Instead of deleting the Vocal Staff, edit the Group Attributes to include it in the Piano Grand Staff.

Then, Reorder Staves using the Staff Tool > Staff Menu to place the Vocal Staff between the Piano Grand Staff.

Edit the Staff Attributes for the Vocal Staff and deselect everything except Lyrics. While still in Staff Attributes, under Independent Elements, edit the Notehead Font and choose the "HIdden" effect. Confirm selections.

Next, select the entire Vocal Staff with the Staff Tool and choose "Respace Staves" from the Staff Menu. Enter "0" in the "Set to" field to superimpose the Vocal Staff onto the top Grand Staff.

Alternatively, instead of having the Noteheads hidden, you can change the Notehead Character using Utilities > Change > Noteheads and selecting Slot 32 (empty slot). This will allow the lyrics to space better.

thanks for your help, I'm going to try your tips!

I'll tell you

Thanks again for your help!

Well done, George!