With the interest accrual there are entries at the 1st and last dates of each month, is there a way of making this so there is just one entry per month, calculating at month end?

These dates actually depend on the date of the lease.

The accrual at the end of the month is calculated so that this is the amount that is included in the monthly journal for that lease. If the lease payments were on (say) the 10th of the month then you'd have 20/21 days accrual until the end of that calendar month in the journal. The remaining 10 days of interest (in the following month) are then added to that first amount and represent the total interest component of the lease payment that's made on the 10th which then resets the running interest owed to zero until the accrual at the end of the next month.

If you just want full months to show then you can select the date of the lease payment as being the last day of the month and then the calculations will be done in one go with no need for an accrual.