This feature is great for cases, where you created a newer version of your model and you wish to replace the old version in PrusaSlicer without having to set up things like custom supports or modifier meshes all over again.
Right-click on a model in the 3D view and choose Reload from disk from the context menu.
Two ways to access the Reload from disk function
When you re-open a 3MF project file, you can still choose to reload any of the models.
By default, 3MF project files are configured to not save the full path to the source models, as this can pose a security risk when sharing such a file. If the full path is not saved and Reload from disk is requested, PrusaSlicer will ask for the location of the source file.