I am running the latest version in trial mode.
And managed to find a solution myself late last night.
DAE is basically a text file you can edit with any text editor. I changed the material*.tif to my original JPGs and got it working.

I downloaded a few models from the 3D Warehouse to use them in some custom scenery for the new Microsoft Flight Simulator.

To create the models in MSFS, i need to

1. Export them to a DAE file with textures
2. With ModelconverterX convert them to a set of files, readable by the MSFS SDK (bin,obj and xml file)
3. Run them through the SDK compiler to get a BGL file with everything needed to place the objects in MSFS

When i export the objects to DAE, SU creates the textures as material*.tif. For a single object, all works well. I can perform step 2 and 3 and the object is available in MSFS for placement.
Problems start when i add a second object.
Export OK.
Conversion with ModelconverterX OK.
All the textures for the different models go into a single directory for compilation with the SDK. Problem: The previous object has textures with the same name.
I tried solving it by saving the DAE with texture names ( https://sketchucation.com/forums/viewtopic.php?f=323&t=40397 ) but no go, when importing in ModelconverterX, the DAE still searches for the files material*.tif
Any other solutions ?