Thanks. Idea I have is to use OpenSea or OpenStreet map and add calibrated maps from Ozi. So far I only found those hints (in russian)
Code:
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on - GPS-Forum so, more detailed steps, suggestions, links are welcome.

Edut:

With help of Global Mapper created geotiff files from OZI source. Now I have OpenStreet map files and image files. Since I have raster maps of different scale, it would be great (if possible at all) to use different images on different scale on navigator. But starting from simple things, what is the best/easiest way to merge those two sources in to final Garmin img file? Any advice?