1. No idea,
2. What kind of object are you trying to display that text in? In a text object you should be able to place them on separate lines
3. Create a custom theme: Getting started creating custom themes - Qlik Sense - YouTube. You can use this site to quickly build a custom theme: https://sensetheme.com/
Thanks a lot for your suggestion on point 3.
Regarding point 2, I am trying to display that text on a map tooltip. I have written the expression in the data load editor and created a field and trying to display that field on a map tooltip.
Expression : 'Cell Id: '& network_kpi.cell_id &' Site Id: '& network_kpi.site_id & ' Payload: '& network_kpi.total_data_volume_gb
Basically I need to know how newline would work in a data load editor expression.