Is it possible to import field definitions from another file? I have a bunch of fields that took a long time to set up in another database and want to get a copy of them into another database.

Not directly.

What you can do, in go into the file menu and do a save->save as clone.

That will save you another copy with no records, but it will be the same database (including all the fields). Then you can go from there.

A somewhat related technique that I often use to recreate a complex calculation field in multiple files is to simply select and "copy" the contents of the Specify Calculation window. Then I can create a calc field in another file and "paste" into it's Specify Calculation window.

In fact, if you have more than one version of FMP on your machine - or access to FMPDev to make a runtime, you may find it helpful to build up a database of formulae and functions that you can switch to while writing code, to copy and paste chunks of frequently used code back and forth to the calculation window.

The calculation formulae can be saved in text fields in your sample code file, with appropriate keywords and descriptions so that you can rapidly locate code you have written in the past that performs a particular function.

I find this technique particularly helpful for external functions, where the parameter syntax is often complex and the level of support (eg prompts for function parameters) from the calculation dialog (ie scrolling lists) is minimal. However it is equally applicable for nested and compund formulae using standard FMP functions.

If you do a fair bit of work with FMP, four hours setting up a resource of this kind (eg populating it with code content from your previous best work) is likely to save you forty hours over the course of a year.