You can change the line height in library > Options > Template Library > navigate to our template > Edit > tap on the template. Then enable “zoom window return height”, set the value, and tap save. It is only effective on new pages (+ > Insert Page), or if you change the template (... > More Options > Change Paper Template).
It is not intuitive to set the value now because it doesn’t display an preview. If you send me your custom template, I can check the correct value for you.