As stated above, you can only map in either a FROM and TO column, or a combined From-To source column. It sounds like you are trying to import three columns of data where you cannot. You'd have to prepare the data before using the import wizard combining your "route" column with the From or To columns data.
For example, say you have a From, To, and Route columns of information you want to import. The only way you can do this is using a program such as Microsoft Excel. You would create a new column calling it "From-Route Combined" then add a simple formula that combines the From and Route column connected with a hyphen. Now you import the two columns into Logbook Pro, your "FROM-Route Combined" map to the FROM column target, and your existing TO column maps to the TO column.
If you need additional assistance, I suggest filling out a
support ticket and use the Attachment feature to provide the source tab or comma delimited data file you are trying to import.