Change instrument live

I use Cubase Studio in live performance to play different instruments during a song. So I can use VST’s and synths through each other.
Most instruments are recorded on forehand, but during playback I have to play solo on other different instruments.
For example : 4 bars on guitar, then 4 bars on strings, etc…(these are not recorded, but the midi/instrument tracks are ready to play when you activate them).
I only have to switch to the track needed (guitar, strings,…) at the right moment.
Now I do this manually by mouse or cursor via the computer keyboard while playing.
This is very unpractical in our modern world.
Any specialist who knows better ???