This can be done via the ‘Once’ option. You set the time for that night and after the expiration of the alarm it will be auto disabled. At the next usage you re-enable the alarm and if necessary adjust the time.
Some tinkering is required here. Have a look at this guide, step 3 till 5 can be skipped if you pick one of the ‘roon-extension-’ examples provided here. Select an example and download a zip file via the green ‘Clone or download’ button. More discussion about this can be found in this thread.
If you can run one of the examples, you can run the Alarm Clock when it becomes available.