In my first database, I probably excessively used copy and paste records (i.e. Relational ID) or replace.

I noticed the default of the replace function (I suddenly discovered one time that I had a unique Invoice of 480.000,00 euro as I accidentaly replaced all the Invoice N

You just want to get the contents of one field and enter it into another? Use the "Set Field" script step.

I've seen a FileMaker solution where the developer probably never new about "Set Field" it's constantly copying and pasting, so you're always losing the contents of the clipboard! The other big problem is that in order to paste, you have to put the cursor in the field, which means the field has to be included on a layout (ever see a filemaker solution with a hidden field somewhere down in the corner where they hope you'll never find it? )