This formula worked. But the MOD function must be on front instead of at the end. Not sure if you have tried this formula in excel as the above format of formula did not work. Changing as below worked for me.
Thank you.
With(
{
varTotalMinutes: DateDiff(StartDateTime, EndDateTime, Minutes),
varDays: DateDiff(StartDateTime, EndDateTime, Minutes) / 1440,
varHours: Mod(DateDiff(StartDateTime, EndDateTime, Minutes), 1440) / 60,
varMinutes: Mod(DateDiff(StartDateTime, EndDateTime, Minutes), 60)
},
Concatenate(varDays, " days ", varHours, " hour ", varMinutes, " mins spent")
)