Two minor updates(2.6.7 and 2.6.8) for hotfixes have been done recently. Compatibility with ProBuilder 4.x has been improved and the UModeler prefab instantiation issue in code has been solved so now the instance of UModeler prefab is displayed in the scene after being instantiated. Lastly Meshfilter's mesh gets saved as .asset when you export UModeler as .prefab using Export Tool.
For a more detailed breakdown of this update, check out the release note.
Version 2.6.8 - June.7.2019
Hotfix : Fix bug where .asset file wasn’t created when exporting to .prefab using Export Tool in UModeler.
Version 2.6.7 - June.5.2019
Hotfix : Improved compatibility with ProBuilder 4.x for displaying icons without overlapping and UModelerizing ProBuilder Object with deleting ProBuidlerMesh component.
Hotfix : Fixed bug where UModeler mesh is missing after instantiating UModeler object at runtime. Added UModeler.Builder() in UModeler.Start() message to have the mesh updated when UModeler component starts.