<< However, if you use the audio editing in BIAB, the track will change color, so you can no longer follow the chord changes.
I actually only want to use Multiriffs to achieve a more flexible mute function, instead of having to start from the beginning of each BAR >>

That's correct and it's normal behavior. Your idea conflicts mutltiriffs, editing and arranging. You must come to the understanding that the editing you do does not exist in the BIAB program or anywhere on your computer before you create that edit. Edits change color because you have created new audio material. In order to keep the editing changes you've made, this new audio must be preserved somewhere and saved in a way that BIAB recognizes it and loads it whenever you open that file. To fix this, decide on what the chords will be and input those chords to use, then apply multiriffs and edits because they are arranging tools.

PG Music has only served to confuse you by adding the Silence button to the Multififf page. It is only there for the convenience to use RT1152:Silence into your arrangement. It does not create a true multiriff. By definition, a muliriff creates multiple renders of an audio phrase (up to 20) where each render differs from every other render. Using silence does not make multiple and different versions of silence. There is only one silence and it is not an audio phrase. The Multiriff tool is not designed to do the job. It's the wrong tool. There is no shame is learning to use BIAB the way it's designed. Multriff is not an editing tool. It's an arranging tool. BIAB has a very robust Audio Editor and works very much the same as every other audio editor. The Audio Edit Window is the proper place to edit audio.

The proper place to silence the audio on a track is either using Mute/Return to Normal in Bar Settings on the tracks that accept the function or on any track using the Audio Edit Window and editing techniques or using Studio One's editing features to do it. Both BIAB's Audio Editor and Studio One's audio editors can select and silence regions that are less than a bar or beat in length.

In BIAB, both automation or the Silence option in the Edit Menu can select and silence regions less than a beat in length.

BIAB 2025:RB 2025, Latest builds: Dell Optiplex 7040 Desktop; Windows-10-64 bit, Intel Core i7-6700 3.4GHz CPU and 16 GB Ram Memory.