In this case, is it possible to put the bar number  between hooks? Thank
Bar numbers are usually automatically shown in square brackets when a system break occurs in the middle of a bar - I suspect if you’ve inserted a dashed barline, that’s causing Dorico to see it as its own bar (although with the same bar number).
A couple of alternative ideas off the top of my head: aggregate time signatures automatically subdivide using dashed barlines, I wonder if there’s a way of using those in cases like this? Or, you could change the default barline used within flows. Feel free to take or leave!
Your suggestion of a default bar gave me the idea to replace the dash bar with a vertical custom dash line. By deleting the dash bar, the bar number is now between brackets and the custom line is well positioned! I like Dorico more and more.
Thank you again.