Comment réduire la taille de la fenêtre d'assemblage sur Indesign sur mac ?

You should be able to grab the bottom right corner and resize it, you may need to move the window to the left.

If it's still not working go to your InDesign Preferences and there's options there to reset dialogs and also reset preferences. 

If you don't have reset dialogs then reset your preferences 

You can also reset this way

Windows: Start InDesign, and then press Shift+Ctrl+Alt. Click Yes when asked if you want to delete preference files.
macOS: While pressing Shift+Option+Command+Control, start InDesign. Click Yes when asked if you want to delete preference files.
A dialog will appear asking to delete the InDesign Preferences, select 'Yes' on this dialog.
Further info and instructions here if needed:
https://helpx.adobe.com/in/indesign/kb/indesign-preferences-support-file-locations.html