You can add custom fields to the ForeFlight Logbook Template (CSV file) available here:
You will want to replace any of the custom field areas entitled "Custom_(Field Name)" with your own custom field. The supported formats for a custom field are as follows:
Numeric entries provide a keyboard with a decimal point for the entry of numbers. The Counter entry allows for choosing whole numbers using a button to increase or decrease the value. The Hours entry is used to enter time in the HH;MM, or decimal format. The Toggle entry has an on/off switch for that field.
When adding a custom field, the text enclosed in "[ ]" needs to be typed exactly as seen above and is case-sensitive. For example, "[Text]" is correct, but "[text]" is not correct.
Here is an example of how to create a custom field. If you would like a field for noting what type of glider launch was used, you could use the [Text]CustomFieldName" format like this:
Example of a custom field added to the Logbook CSV Template.
When you import the CSV file, that entry you made creates a custom text field within Logbook named 'Launch Type'.
A custom field is shown in LogBook. Text can now be entered.