The daily summary editor
Cumulus maintains, in the 'data' sub-folder, a single dayfile.txt file. The last command in Edit menu is dayfile.txt. If you use this editor and select Create missing button then a new file, dayfileeditlog.txt, is created in the main folder where the Cumulus executable is stored. It logs what Cumulus calculates during this editing. Note if you use 'create missing' again, the file gets overwritten, so you may wish to rename any existing dayfileeditlog.txt file before you use the editor.
List of fields in the dayfileeditlog.txt file
It will have one row for each date that is missing in the original dayfile.txt, but present in monthly log files. A row holds the fields listed here, including highs and lows of that (meteorological) day, calculated from looking at all the records in the Standard_log_files for that (meteorological) day, and the added rows are in chronological order (but without rows for any date that is in 'dayfile.txt').
Cumulus 'Create missing' makes no attempt to create values for 'highest hourly rainfall' but does the best it can with everything else. Normally, what is stored in dayfile.txt is based on every reading received from the weather station, but only the logged readings are available to put as values and timestamps in dayfileeditlog.txt and Cumulus has to assume that these have captured all extremes for each daily summary row it creates. Calculated values that involve a number of original observations (e.g. temperature and wind speed are needed to calculate wind chill) may be particularly sensitive to logging interval.
Exiting the editor
When you press OK, the records listed in dayfileeditlog.txt are inserted (from version 1.9.4) in correct chronological order position into dayfile.txt file. If you press Cancel, the dayfileeditlog.txt is retained, but the dayfile.txt file is left unchanged.
The dayfileeditlog.txt file can be used to see what would be inserted for calculated values like 'apparent temperature', that may not be available for some rows in your dayfile.txt file. However, to do this you need to follow this workaround deleting the incomplete rows in a temporary 'dayfile.txt' before running 'Create missing'. Since Cumulus only updates 'dayfile.txt' when it is doing a rollover, you can change file names or otherwise manipulate the file the editor will work on while leaving Cumulus running. Consequently, if only a few days are affected, you can follow a variant of the workaround where you press 'Cancel' on the unwanted 'temporary' (otherwise known as 'generated') 'file' and open in a text file viewer the dayfileeditlog.txt file instead to give you values to manually insert into the final 'dayfile.txt' in a second use of the Cumulus editor mentioned above instead of an external spreadsheet or other editor.