Is there a way to put the actual key into a song file and use capo chording on the chord sheet?
For instance, actual key of D - capo up two frets - write chords in C?
Hi Ricky,
Welcome.
In addition to Jim's take on your question...
If the reason you are asking this is because you are not comfortable with entering chord progressions in D and would prefer to enter them in C, BIAB can help.
Simply think in terms of scale numbers in C rather than notes. This is the Nashville way of doing things and BIAB responds to it by default. It's called the Nashville Number System (if you haven't heard of it before and want to look it up) and it makes writing in every key easy.
For example say you're in D and you want to have the equivalent chord progression for C Am Dm G7. On a piece of paper write out the numbers 1 - 7 and align them with the notes of the C scale (see image below).

Using the above, C Am Dm G7 converts to 1 6m 2m 57 so simply enter the chords using those numbers in the key of D. BIAB will automatically respond by adding D Bm Em A7 to the chord sheet.
I thought I'd mention this in case it was this aspect of using a capo that you were after.
Regards,
Noel