I’ve set up a Project with the Layout Options / Page Margins set to 0 and the margins themselves defined under Page Templates. This enables me to set a different background colour, right to the edge for the Page, for Lyric pages. I can then factor in the Page Margins to the remaining Page Templates.
However, I’ve found a problem with this approach - the Engrave Mode Gap Measurements are no longer editable. Clicking on them switches the view back to Write Mode. The handles at the edges of Objects are editable (which in turn updates the measurements) - but not the measurements themselves.