How to convince Remmina to use two displays in a three monitor setup

I have two external monitors (both 1920x1200) connected to a laptop. I'm connecting to a Win10 (with also two monitors on its PC) via Remmina, with an *.rdp file supplied by Citrix Netscaler Gateway.

• Every application that's maximized in the session takes all the space of both the displays and
• centered dialogs/apps appear in the maximized center, i.e. are spread aside the physical middle of the two monitors.

That's bad.

1. Can I convince Remmina to consider the two monitor setup on the remote system so that maximizing inside the session just uses one of the local displays?

2. Can I convince Remmina to open new (centered) windows/dialogs centered on the first local display (without a Window Rule [see additional info below] for each and every)?
   [Solved implicitly if 1. is solved.]

3. If 1. and/or 2. isn't possible natively I have another idea:
   Can I connect with two sessions, one using the first remote display and one using the second?

There's a Multi monitor button in Remmina's session toolbar. But it:

• does nothing when activated in full-screen mode,
• then scrambles my displays when switching from full-screen to windowed mode (and also back to full-screen mode)
• and even terminates the connection without further notice when activated in windowed mode.

Additional information (for potential future seekers, readers, attempters)

At first I struggled to convince Remmina to take all space of both the external monitors for the session (including/overlapping the space of the local bottom panel). I managed this via:

1. A Window Rule

   Created via Right-click Remmina's title bar➔More Actions➔Configure Special Window Settings.

2. Session toolbar

   • Toggle fullscreen mode (Default: Right-Ctrl+F, I changed that to Scroll+F since Ctrl+F is standard for Find in so many applications).
   • Toggle dynamic resolution update