Quote - One thing that's still not clear to me is, how to get any of the (custom) V4-Charcters into Genesis.

Straightly asked:

If I look at the right side of this website, I see the "What's Hot Today" ads. In there I see "Betty for V4 .. " by Vyktohria. (Just to use her as an example, for my question).

How would I get "her" (or any other character on that matter) into Genesis in Poser?

Can someone please tell me how this could be done, and what else, beside the installed DSON-Importer, i eventually would need to accomplish this?

You would need GenX from Dimension3D

After you installed it, there are several ways to go, but this is the road I take

In DS4.5 you drag V4 into GenX, then you drag Base morphs into Genx, then morphs++ and any other pack the character needs in Poser.

After you have done that, you choose with the Select button Transfer:On for all Non-zero values. In the box next to it you select "Selected morphs with preset"

Now press transfer - then it will prompt you with a location to store your preset for the character. Choose a location which you can access from Poser (in one of its runtimes)

Now - here the tricky part. If you have not shared your DS4 runtime with poser but another one (specified in the essentials installation), copy the genx morphs which were created in DS4 to that runtime. Same relative location. It is in the data folder of DS4 (in my case it is DS4dataDAZ 3dGenesisBaseMorphsD3D Gen X)
There are several data folder in my DS4 and you have to find the right one. Use exactly that location

After that you can load Genesis and apply the preset. Then use Basic Female (or Mec4Ds script) to change UVMAP to V4, then apply the V4 mats

That worked for me (after some experimentation)