Then, I realized that I can’t really delete the barline beside the time signature. When I press delete, it just does nothing.
Please help me, is there a way to delete or hide the barline beside the time signature?
Welcome to the forum, 4841283llao (catchy screen name ).
There’s no built-in way of doing this (though showing range indicators at the start of the vocal staff would be a nice feature for Dorico to have in future, I think), but it’s possible to do reasonably easily provided you don’t need dashed barlines anywhere in the piece. Select the initial time signature and in the Bars and Barlines panel on the right-hand side in Write mode, choose a dashed barline. Then go to the Barlines page of Engraving Options and set ‘Dash length for dashed barlines’ to 0 spaces.
Create a 5/4 for the very first bar and a 4/4 for the second bar.
Hide the 5/4 time signature in engrave mode.
Then, in engrave mode, “drag” the 4/4 time signature from the second bar to the first bar to pretend that “4/4” belongs to the first bar.
It would be computationally a lot more expensive to do it for all flows, and not very Dorico-like (given that flows are completely independent). The problem in general would be keeping it up-to-date efficiently because potentially every edit made to every note could change the range calculation.