You can import Gerber and drill files in PCB Layout. But this won't recover original PCB design in full. You will get many shapes, pads and holes but won't get them as components, nets, traces and copper pours.

Thank you for the feature request.
"Depending on board" trims or expands copper pour regarding on if you created the copper pour bigger or smaller than board outline.
"Snap to Board Outline" option does the above changes automatically once you edited board outline.

In order to get correct BOM and Pick and Place files, it would be better to have mezzanine connector and studs separately instead the composite component. Further in PCB Layout you can group them to operate with items as a whole.

Select two layers at once (board outline and a layer you want to export) then click "Export Layer" button.

We aware of the problem but this seems a Wine issue. The same executable works differently on Windows and Linux. All we can do is to recommend stable version of Wine and 32-bit version of DipTrace even though you have 64-bit system.

Thank you for the report, I see the same. We will investigate whether it's a problem or not as changing layer type to mixed doesn't forbid traces on the layer.

Hello Allen,
Please check design rules. The clearance rules are too strict - 6 to 20 mm. With theses rules interactive router can't even start routing. Once you change the rules to more realistic you will be able to route traces.

How did you get slot holes in PCB? I mean did you use pads with oval holes or shapes on board cutout layer? In the first case, do not forget to turn on "Pad Holes' when you export STEP. In the second case, you should get the same result in STEP file as you see on 3D preview.

Via stitching and via shielding tools don't place vias on pads because often this is not good practice to do. But you can place vias on pads manually and connect the vias to the same net as the pad.