I'm trying to create songs with, e.g., 6 choruses, with melody in first and last choruses, solos in the middle choruses and one middle chorus with no solo to leave space for me. That should be all pretty standard, I think.
I'm not sure where you are at right now, but I'll explain that there are a couple of different approaches you can use. To summarize the two mentioned in this thread (1) using the Bar Settings dialog to mute certain regions of the song, or (2) creating a medley.
I really like your idea of creating a medley to accomplish this, and it is extremely simple once you know how. Often people would be using different instruments in a medley, but that's certainly not a requirement; you can have a medley that alternates between "silence" and a RealTracks Soloist. The reason I prefer this method over bar settings, is because it will give you more natural transitions between a chorus that doesn't have a solo and one that does. (e.g. muting a chorus might cut off a solo mid-riff).
(BTW I'm talking about the Solo track, not your melody track, since I don't know what your melody is)
Let's say you have 6 choruses and only want the solo to play in choruses 2, 3, and 5. Here's how:
1. Right-click on the Soloist track --> Select RealTracks (technically you could do this on any track, but the Soloist track makes sense). This opens the RealTracks Picker with the Soloist track selected.
2. Choose your RealTracks soloist. In my case (see screenshot below) I wanted a Sax solo, and chose "Sax, Tenor, Jazz Sw 140". (further explanation.. it isn't necessary to choose a specific RT here if you will be making a medley for the track since a medley can have ANY combination of RT's, however this DOES set the default instrument for the medley, so you may as well choose the one you want)
3. Click the Medley button. Set "Change to a new RealTracks every CHORUS". Each of the entries in the list now represents a chorus.
4. For the first entry (chorus 1), choose "Silence". For the second, choose "Sax, Tenor, Jazz Sw 140". Repeat for the remaining choruses, and you should have something that looks like this:
5. Press OK to exit the Medley dialog, and press Close to exit the RealTracks Picker.
Here is how to use the bar settings method.
1. Right-click on Soloist track --> Select RealTracks, choose the RT that you want and press Close.
2. Click on Bar 1 and press F5 (Or Right-click and select Bar Settings).
3. At the top of the dialog "Settings Apply to Chorus #" select "Chorus 1"
4. In the "Instrument changes this bar" area, set the Soloist ("Sax" in my case) to "Mute".
5. At the top of the dialog "Settings Apply to Chorus #" select "Chorus 2" and set it to "Back to normal". Repeat for Chorus 4 and 6.
For completion, here is one more option you have that IS specific to the Soloist track - if you want to Solo only in the middle choruses (no solo in choruses 1 and 6). Soloist menu --> Generate and play solo. Select the RealTracks instrument (note that this dialog also has MIDI soloists in it - the RealTracks instruments start at 361 and color-coded beige). Set "Solo which choruses" as appropriate, and then press OK.