I believe that amendments to the CA constitution have to be voted on by the public. But Californians voted for the Jungle Primary system which means you have many elections with no Republicans on the ballot, so who knows.
On the other hand, the US Constitution requires the Federal Government to ensure that each state has a republican (small R) form of government. A secret legislature might run afoul of that provision.
A secret legislature might run afoul of that provision.
That won’t stop them.