Create different tracks:
Guitar Pro supports more than one "voice" for each track.
Each Guitar Pro staff contains two independent voices in the case of GP5, and 4 for GP6. This type of notation is thus closer to the standards of musical notation.
To edit a voice, choose the "Edit > Voices > Edit Voice 1" or "Edit > Voices > Edit Voice 2" menus (or voice 3 ...
Your guitar is now a Bb guitar = tuned down a major second. The E strings are tuned in D and also all others are a whole tone lower.
The notation is like you would read it if the instrument would be tuned in C. The instrument is transposing these chords from G down to F.
This is quite the same like the music written for all Bb-instruments like trumpet, ...