How to access a second sequens list in a preset

I'm really not sure what you are trying to do.

You can use Action Macros to send specific commands to Masters:

For example, the Action Macro "Go M1,201,5" will tell Master 1 go Goto Preset #201 with a 5-second fade time - as long as it has a Sequence including preset 201. (If it doesn't nothing happens.)
If you don't include the time it'll use the time recorded in the Sequence Step, and if you don't include the Preset number either it just does a basic "Go".

These Action Macros can be put into any Sequence Step, attached to Triggers (contact closure, serial or 'raw' MIDI) or sent directly over OSC.

Another method is to use MIDI Timecode.
Any Sequence on the Main Playback or any Master will follow the timecode being sent to the console when Timecode is enabled.
So you could have QLab output MIDI Timecode, and have a Master contain a Sequence with the steps each having the appropriate Timecode time.

To record timecode times in the first place:
Put it on Main Playback temporarily, open the Timecode dock and use the timecode "Learn" button to start recording.
Then play the QLab timecode and hit [Go] at the right moments. Once Learned the timecode is stored in the Sequence Steps so you can use it on Main or Master Playbacks.

Yet another is to use General MIDI to press the Master Keys and/or Flash Buttons to play the appropriate items.
If you do it this way, remember that Note On means "press key" and Note Off means "release key", so the key will remain held down until the appropriate Note Off is received.

My guess is that MIDI Timecode is probably the best way, although I'm really not sure what you want.

I'm really not sure what you are trying to do.

You can use Action Macros to send specific commands to Masters:

For example, the Action Macro "Go M1,201,5" will tell Master 1 go Goto Preset #201 with a 5-second fade time - as long as it has a Sequence including preset 201. (If it doesn't nothing happens.)
If you don't include the time it'll use the time recorded in the Sequence Step, and if you don't include the Preset number either it just does a basic "Go".

These Action Macros can be put into any Sequence Step, attached to Triggers (contact closure, serial or 'raw' MIDI) or sent directly over OSC.

Another method is to use MIDI Timecode.
Any Sequence on the Main Playback or any Master will follow the timecode being sent to the console when Timecode is enabled.
So you could have QLab output MIDI Timecode, and have a Master contain a Sequence with the steps each having the appropriate Timecode time.

To record timecode times in the first place:
Put it on Main Playback temporarily, open the Timecode dock and use the timecode "Learn" button to start recording.
Then play the QLab timecode and hit [Go] at the right moments. Once Learned the timecode is stored in the Sequence Steps so you can use it on Main or Master Playbacks.

Yet another is to use General MIDI to press the Master Keys and/or Flash Buttons to play the appropriate items.
If you do it this way, remember that Note On means "press key" and Note Off means "release key", so the key will remain held down until the appropriate Note Off is received.

My guess is that MIDI Timecode is probably the best way, although I'm really not sure what you want.