To anyone interested in rendering overview maps of worlds on Pocket/Bedrock Edition.
There is a quite new tool Papyrus.CS
It is listed on Gamepedia: https://minecraft.gamepedia.com/Programs_and_editors/Mapping
(there is also listed similar tool Papyrus.JS, however it works only on Linux)
Papyrus.CS works on PC only (Windows or Linux), however it may process any Pocket/Bedrock world
(a "pocket" map may be simply copied to PC computer, into the folder where Bedrock worlds are stored).
I tried this tool and it works OK
The maps are generated as scripted HTML pages, so they are convenient to use (zooming, panning, coords, etc.)
The problem is that the map is generated only for the already discovered areas of the world.
It would be useful to use another mod first, which would "travel" through the world and "discover" a consistent large area, and only then we may generate the map by using Papyrus.CS.
I'm just trying to write such a "traveling" mod by myself...
however maybe anyone knows if such a mod already exists for Bedrock edition ?