Based on our analysis and surveys it has not been used too frequently.
So to not overload the OS with options that are not used too much (not only does it save space, but also improves the overall performance), this option has been removed from Android 10.
You might create a suggestion here on the Beta Community (in Suggestion section). If it gains a lot of support, then our development team will reconsider this for sure!
Me too.. Just signed up for beta. Was one of the first things i noticed. I have all my grids on max ( 5x6) etc.. Hopefully they'll reintroduce it on final build