How do I get rid of this black box?

Hi @Mr. Met:

I think Colin and Leo are both right: you have disabled the Home Screen When No Documents are Open (as per Colin) and the Application Frame is covering your desktop (as per Leo). And you pushed your tools/panels as far off to the sides as possible!

~Barb

Not sure I understand you correctly, but will disabling the application frame (Window > Application Frame menu) do what you need?

What Mac OS are you using? At the present time most Creative Cloud apps (including InDesign) are not fully compatible with Sonoma. See https://helpx.adobe.com/download-install/kb/macos-sonoma-compatibility-common-issues.html for a list of the apps that are now compatible. If you are on Sonoma then try to go back to Ventura version 13.6 (not sure if that's possible).

If you aren't on Sonoma then if you used the option to import previous settings and preferences when you installed CC 2024 then that could be the problem. Using old preferences that were compatible with the old version has a track record of bad performance. Try trashing your InDesign preferences. This will bring the program back to its defaults which, hopefully, will fix the issue.

To trash preferences on a Mac:

The User Library folder in which InDesign’s preferences are stored is hidden by default on most Macintoshes. To access it make sure that InDesign is closed and click on the desktop to launch a Finder Window (Command-N). With this window in column view follow the path User>Home folder (it’s the folder with an icon that looks like a house—it may have the user’s name rather than “Home”) and click on the Home folder. With the Option Key pressed choose Library from the Finder Go Menu. “Library” will now appear within the Home folder. Within the Library folder find the folder called Preferences and within it find the folder called “Adobe InDesign” and the file called “com.adobe.InDesign.plist” and delete both that folder and that file. When InDesign is next launched it will create new preference files and the program will be restored to its defaults. 

The advantage of manually deleting preference files in this manner is that after you’ve reset up the program (make sure that no document window is open) to your liking, you can create copies of your personalized “mint” preference files (make sure that you quit the program before copying them—that finalizes your customization) and use them in the future to replace any corrupt versions you may need to delete.