Steps: Quotes in "start_step" are visible to Partner Users, How to restrict the quotes?

We want to restrict set of quotes created by the X group users (host company), that should not be visible for Y group (Partner Org users).

Group of X is creating quotes on production, which is up and running, now we are introducing new group Y, which are partner users.

Scenario,

1. X group creating quotes which are moved from Start step to next steps, which are restricted to the group Y (Partner users)

2. If X group creates any quote and still in the Start step, then that quote is visible to group Y (Partner users) -

3. Because of there is no option to select group in the Steps for Partner users we are not able to restrict the quotes created by X group (No forwarding rule applicable in start step)