For example, if I wanted to always see rows 5, 10 and 15, as far as I can tell, I would have to freeze every row from 1 to 15. But is it possible to only freeze the specified rows so that if I scrolled down, the first four rows could be 5, 10, 15 and 20.
Why not just arrange rows 5, 10 & 15 to be rows 1, 2 & 3 and freeze the top three rows? If needed, move then back to 5, 10 & 15 after you’re done or leave them.
You could also just duplicate the lines. Have the maintainable content in lines 1-3 and add additional lines in lines 5, 10 and 15 which refer to the others via formula (or vice versa If you prefer to edit 5/10/15). To avoid that you change the wrong lines by mistake, you can protect the cells with sheet protection.
I thought about that as well but I found a better solution, which is to just move the rows to a different sheet. I don’t need the rows to be on the main sheet, I just need them to be visually next to each other without breaking the structure of the spreadsheet, which moving them to a second sheet would do.