By default, PrusaSlicer places the bottom-most point of each object on the build plate.
In the vast majority of cases, this saves the user time and prevents possible failed prints, where the model would be accidentally slightly lifted above the print bed. However, in some cases, you might want to lift an object above the print bed on purpose. For example, you might want to add a logo or text on top of another object.
The way to do it currently is to use a multi-part object. Only the bottom-most part of a multi-part object will be placed on the build plate. Other parts can be lifted from the build plate freely.
You can also create a multi-part object by merging multiple objects together
When you click on a multi-part object in the 3D view, all parts will be selected. Use the Object list in the right panel to select individual parts.
Contrary to other slicers, PrusaSlicer slices each object independently and it also builds supports for each object independently. This approach is beneficial in many ways, it allows us to do tricks like variable layer height, support stepping independently per object or reslicing only part of the scene when a parameter changes to save time. On the other hand, it also means that objects, and more importantly, supports from two separate objects can collide. Placing one object on top of another and enabling supports would counterintuitively build supports through the bottom object, which would be difficult to see in the preview and ruin the print. Indeed, intersecting supports for objects placed close together is relatively frequently reported as a bug even now.
In addition, the assumption "objects are not floating" is present in many places of the codebase, and there is no simple way to simply allow lifting objects up without breaking many of the existing features.
To summarize, in order to enable this in the future, we will also have to implement:
With that, the user will get meaningful feedback if the print is not printable (floating in mid-air or having overlapping extrusions) Implementing all of this will be fairly difficult. With some more requested tasks from the community having a higher priority for us, we have no estimated deadline for implementing this.