Each reservation in myfrontdesk has unique reservation ID number, but it's not included to reservation URL. For example, Reservation with ID 8851209151 in reservation URL ends with 5701810.
For some applications you would need to have a custom link with booking exact ID to jump straight into the specific reservation's details page on Cloudbeds.
You may create a custom link with myfrontdesk reservation ID as shown in example below
so, for mfdID you enter the ID of your property, and for XXXXXXX you enter the reservation ID right after letter 'r':