Not that i can see. The declare’d query isn’t shown to accept $n bindings rather it must be executable (select or values). Per the note on declare, the bind phase of the fetch command under the extended protocol is used to determine whether values retrieved are text or binary. Beyond that, the bind is really just a formality of the protocol, the same as for executing any other non-parameterized query that way.
Seems you can bind to the Declare though.
execute <unnamed>: BEGIN
2024-07-10 11:18:57.247 EDT [98519] LOG: duration: 0.239 ms parse <unnamed>: DECLARE c1 CURSOR WITH HOLD FOR select * from vactbl where id < $1
2024-07-10 11:18:57.247 EDT [98519] LOG: duration: 0.014 ms bind <unnamed>: DECLARE c1 CURSOR WITH HOLD FOR select * from vactbl where id < $1
