Can a group of lines (a poem) be formatted as a style?

Writer 4.2, iMac latest version, English,

IMHO you can.

I would create a new paragraph style starting from the default style and modify it until it matches the way I want to have a verse displayed. This style settings can also included the space you want to have in front and at the end of each verse.

I also recommend to read the free Writer manual:

I use two paragraph styles to manage a poem. The first is a heading( for example SONNETHEADING) to provide the poem TITLE, font, space above and below the title and indexing information to add the Title to my automatic index. Then you can link this style to the general poem style (for example SONNETBODY). This again gives the font, centered etc. With new line you can create your poem. I use the same technique for each type of poem, sonnet, haiku, limerick, plain poem etc. (My brother is a poet. )

This way one can create a single poem, and then later build them into a book without having to change the source poem itself. good luck