If Merge (Fusionner) and Place Hotlinked Module are gray / disabled as in your screenshot, then you are either in the 3D window, or if you are in the 2D window, you are the middle of drawing something with a tool.
Your screenshot shows that you are in the 3D window.
You must place your module in plan view (2D). You can then drag it horizontally to align with your other modules as desired. THEN, you can open 3D and and elevate the module to the proper height relative to everything else.
Note: You can create a special layer to control the visibility of each module. So, while each module has walls in the WALLS layer, if the master layer for each module is unique - MODULE A, MODULE B, MODULE C - you can turn all walls off in all modules, but hiding the WALLS layer - or you can turn the entire B module off by hiding the MODULE B layer. This is called the "Master Layer" in the Place Module dialog ... which you will see when you try to place your module from 2D/plan view.
Well, your stories will in essence be disabled if you only have one of them.
🙂
Cheers,
Karl
One of the forum moderators
AC 28 USA and earlier • macOS Sequoia 15.2, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB