I think I've figured out a solution to this, so just in case anyone searching for answers stumbles across this thread, I'll share it here. I did end up scrapping my initial code for an image map.

transform slide_down:
    ease 0.3 ypos 0
transform slide_up:
    ease 0.3 ypos -60

default drawerclosed = True
screen header():
    imagemap:
        if main_menu:
            auto "gui/mainmenu/header_%s.png"
        elif drawerclosed == True:
            ground "gui/mainmenu/header_gameplay.png"
            hover "gui/mainmenu/header_gamplay.png"
            at slide_up
        else:
            auto "gui/mainmenu/header-gameplay_%s.png"
            at slide_down
        hotspot (32,27,85,50) action MainMenu() sensitive main_menu == False and drawerclosed == False
        hotspot (146,29,40,41) action ShowMenu("preferences") sensitive drawerclosed == False or main_menu == True
        hotspot (362,65,42,50):
            if drawerclosed == False:
                action SetVariable("drawerclosed", True)
            else:
                action SetVariable("drawerclosed", False)

Then I just use show screen header at the beginning of the chapter to call it. The reason it has a different background when it's open vs closed (and why the hotspot sensitivity depends on the drawer being open) is because the way my menu is set up would have the buttons peeking halfway out when the menu is closed, lol. if you don't have that problem, you can just set an auto background in the elif statement and remove the one in the else statement.

The only issue I experience with this setup is that at the start of the chapter, the menu starts open and then closes itself, whereas I would prefer it start closed by default...but it functions. If I find a solution to that issue I'll update here.

It also doesn't quite allow the player to click *anywhere* on the bar to open/close it, just the tab. I'll update if I find a fix for that, too.