MuLab Plugin is very versatile: You can use it as a synth, as an effect, as a composer, or as any hybrid combination of these.
For example an audio filter controlled by a step sequencer, or a 2 track composition that plays a bunch of audio sequences, layered on top of your main host DAW composition. Now if you use MuLab Plugin as a composer, then the question that pops up is: How to sync its timeline to the timeline of the host DAW?
There are 2 ways:

1) Using the "Sync" button at the right of the transport.

When this sync button is activated, MuLab Plugin will sync to the timeline position as the host DAW.
Right-click that sync button for specific options.

Note that this syncing is only done upon starting/stopping/repositioning the host DAW, depending on the sync options you've set.
Once playing MuLab follows its own clock time.
This also means that if you want to loop a section you have to set the loop in MuLab too, which can be different from the host DAW loop, which is a creative advantage.
Both the host DAW as MuLab use very precise clock counters and so things will practically play in precise sync.

If the host DAW and MuLab Plugin have been playing in parallel for a (very) long time, there might be a tiny little drift between the 2 clocks, because they each use their own clock algorithm and/or due to floating point rounding errors that build up.
Most of the time this will not cause a musical problem because both clocks are very precise.
Now in case you want the very most tight sync (eg when sending parallel notes to both host and MuLab Plugin and want to avoid flanging effects) then enable the Beat Lock option.
This will make MuLab Plugin constantly watch the host DAW clock and make sure that the syncing stays as tight as possible, even after hours.
This option is enabled by default.

Note: In case you would want MuLab Plugin to use its own tempi and so that its timeline play cursor progresses in a different way than the host DAW play cursor, only in this case the Beat Lock option is not to be used, but that's quite logical.

2) Using Note Event Actions.

Note Event Actions are special event mappings that let you say for example:
Upon receiving note C2, start playing the timeline at bar 5, upon note D2 loop the timeline from bar 17 to bar 33, and upon note E2 play Live Matrix scene X.
This way you have precise and creative control what has to be played when.
And so that's an intersting option to sync MuLab Plugin to the host DAW, in an even more controlled / creative way.

See the Note Action Map doc page.

More Info

• Note that once MuLab Plugin is playing it will keep playing on its own clock until stop.
  In some host DAWs clicking play and then again clicking play without stopping the host DAW won't resync MuLab Plugin.
• Shift + Right-click the sync button opens a diagnostic data monitor window where you can see what info the host DAW sends to MuLab Plugin.
• Cantabile 3 (dd. 2022.02.16) does not provide correct timing info to VST plugins.
  That's why MuLab Plugin cannot properly sync to Cantabile.
  More specifically: Cantabile gives an incorrect VstTimeInfo.samplePos (cfr tech definition and notes in aeffect.h) to VST plugins.