Currently there is a Billboard Anywhere mod, which uses a hotkey to access the community calendar. But what about the Bulletin Board which announces quests? In theory, it should work, and when there isn't a quest it would just show the "nothing posted here" notice. I don't know how to "unravel" a SMAPI mod DLL file or else I'd try my hand at it myself.
Unfortunately, you can't unravel a DLL file, it wouldn't show you the original code files that it compiled. The best thing you can do is ask the creator if they're willing to post their source code. Though, I would say not to expect 100% that you'd know what to do from looking at the original code, you may find you'd still struggle to show the quest bulletin versus the calendar one because it'd involved different coding to invoke either one. Mainly, you'll need to figure out what already programmed methods, in the Stardew Valley library that you reference, are already given to call upon the quest bulletin.
I was using the Billboard Anywhere mod, but I ended up switching to Calendar Anywhere instead 'cause I am starting to have too many assigned hotkeys and it was getting confusing. With this mod, all I need to do to open the Calendar is click the icons on the top right corner (between the date and the time). As for the quests bulletin, I'm using DailyQuest_Anywhere.
