Here is @rextended workaround layed out with commands and all:
For device without flash remove the “flash/” prefix in the filename (in BOTH places):
step 1: make backup
/system backup save dont-encrypt=yes password=123 name=flash/confgbackup.backup
step 2: plan script to restore backup in System/Scheduler (choose whatever time you need):
/system backup load password=123 name=flash/confgbackup.backup
:delay 2
:put y
step 3: make changes
step 4: if the changes are good, remove the restore script from the scheduler, otherwise wait for the script to trigger a restore of the backup