The 4x4 hollow square on the left on the config page is unchanged from 1.6.1: it toggles note sync (triggers are placed when you place a note, and loop positions are synchronized). The change is that this used to be linked to loop sync, so you had to have loop sync engaged in order to use it ā now you can have note sync on (triggers and notes share a loop and are toggled together) but loop sync off (all parameters besides trigger and note can have independent loop endpoints, but trigger and note share a loop). This is orthogonal to div sync, because note sync as of 1.6.1 does not link clock div changes, only loop points.
Division sync and note sync are settings for groups of parameters rather than individual parameters, so I think you would need a 7x7 matrix to represent all possibilities. But this would be super flexible! Consider the following hypothetical UI:
Config page, i.e. holding KEY 2: existing UI, to provide for normal note sync / loop sync configuration, but with three highlighted keys in the same position as the Kria mod keys: loop, time, and probability. Press one of these keys to go to the Sync Matrix page.
Sync Matrix page: The left half of the grid is the sync matrix for the modifier you selected. The mod keys are still highlighted, with the currently selected modifier brighter to show itās selected. You can press one of the others to go to the sync matrix for that modifier instead. Above this on the right half of the grid is an additional 4x4 matrix controlling linkage between tracks. Press KEY 2 again to exit the Sync Matrix page and go back to the normal Kria sequencing UI.
The sync matrix is a 7x7 matrix of toggles in the bottom left corner, corresponding to the 7 Kria parameters. This allows you to toggle on and off which parameters should be linked, whereas the 4x4 matrix on the right lets you link linked parameters between different tracks.
These matrices have a couple properties that mean a full 7x7 or 4x4 square is not a very efficient use of grid space ā the diagonal will always be on, for example, because a parameter or track always shares linkage with itself, and the matrix will always be symmetrical. So I think this means you only need the lower triangular part without diagonal to capture all the state, but this may not be as intuitive as using a matrix display. I think this approach generalizes all existing sync modes, (as well as adding the possibility for probability syncing between parameters?), with one exception ā note sync causes placing notes to place corresponding triggers as well as loop endpoints. You canāt capture this with just the sync matrix for Loop, and I donāt think it really makes sense for other pairs of parameters. So maybe the note sync glyph would mean āI also want placing notes to place triggersā and it would be possible to toggle this separately from using the sync matrix to link these parameters.
Iām not sure Iām explaining this well and it might wind up being suuuper confusing, but I think it might not be too hard to implement 
P.S. what did you use to make this UI mockup? Iāve seen a couple different ones now but my searches are not immediately forthcoming with what software people are using.