How to Concatenate 2 Values for the Preview Title

hey all, is it possible to concatenate 2 values for the

preview

title ? In my case I'd like to merge the number into the title such that it could appear on the left as "172 - Il faut que tu ruines tout". Thanks!
Second question, is
this really the only way to go about creating singleton pages in Sanity? seems awfully convoluted.. there must be a better way, no?

You can use

prepare()

to reformat your preview, like this

You can use

prepare()

to reformat your preview, it’s all well documented here: https://www.sanity.io/docs/previews-list-views