How to edit and fix an skeletal mesh modeling problems, i.e., wrong normals, tessellation, etc. in UE

I would like to ask you a question: how can I fix minor issues of an SKELETAL MESH like: tessellation, normal and pivot point positions, etc. in UE .

I need to fix the Skeletal mesh in UE, otherwise I have to go back some steps, fix the model in Blender and reimport the model. This is a time consuming process and I might loose some works I have already done in UE. Therefore, I am trying to fix the skeletal mesh in UE.

The skeletal mesh is a car I designed and modeled in Alias, exported to Blender to rig, then imported to UE to animate using Control rig and Sequencer. The pivot points of the wheels needed to be moved, also the mesh shows some minor issues that I guess caused by wrong normals and tesselation, etc. The model is merges, i.e., is a one asset.

To fix the minor issues of the model, i.e., Skeletal mesh, I found that UE Modeling mode might be very helpful. But, when the skeletal mesh is selected, the majority of the tools in the corresponding Toolbar are grayed out. What should I do to activate the grayed out tools?

And if I use Transform>convert tool, as on of the few active tools (not grayed out), I will have a static mesh with no bones, accordingly no control rig and animation. Although using the Convert tool fixes all the issues of the skeletal mesh automatically.

I also tried to export the converted mesh (now converted to a static mesh) as fbx and import again. Although by importing the fbx, UE creates an skeletal mesh, Physics asset and skeleton, but bones are missing.

Moreover, I tried replacing the mesh of the skeletal mesh with the converted and fixed mesh, but it did not work. As soon as I replace the mesh, the issues appear again.
Thanks a lot for your help and advice!