Sometimes people are confused between transposition and modulation, but they are completely different.
The former we have already discussed. The later, modulation, is about the changing keys in a song.
Transposition is used as an option for arranging music and is considered to be a technique for musical expression.
If "modulation" occurs, the number of chords will increase. Since increasing the number of chords is a heavy burden, it is better to avoid songs with modulation.
Modulation will often appear in prelude, interlude and postlude, or in some chorus sections that are not so important.
In this case, the best way for beginners on Qactus is to skip learning this section of a song.
So for those of you considering to make the QactusCore, there are several things you can do to help others.
QactusCore has a message column so we can give suggestions like: "The part after the interlude can be skipped if you are going to play with Qactus as a beginner."
If you face chords called Secondary Dominant, you can generally put  in The Gray Room.
This kind of chord will be a little hard for beginners on QactusCore, but it’s worth playing for the effect.
Arranging into acoustic guitar versions are also useful as well as cutting the boring section or parts that is too difficult to play for beginners.
Also, experts, please try to decrease strumming for beginners.