@LeiLar,
You are right this is possible. However, I think it is not easy to use even if you have set it up fully.
The way I do this is based on the GPS track in the Android device.
The simplest way is to do the walk yourself (can also by bike or car) and record the walk in the device. Some instructions can be found here: http://code.google.com/p/osmand/wiki/HowToArticles
Alternatively you can record the walk on a GPS device and store it in the following directory: \OSMAND\tracks.
Third method is what you seem to have in mind. Use the navigation of OSMAND. In your case you need to know well how to evaluate the outcome, as it does not always do logical things for the setting "walking.
Select the “destination” on the map (keep your finger on the screen where the destination should be en select destination”.)
Select waypoint 1 (keep your finger on the screen where the waypoint should be en select waypoint”),
and so forth until you have selected the last way point.
Finally keep your finger on the start point on the map and Select “show route from here”.
OSMAND prompts you for the type of route, select walking and wait till the route has been calculated (now its your time for coffee ;).
It will show you the track and you have to verify it!!! If it has unwanted parts, you have to take points out and try to redefine it, till you have a satisfying route.
Open Route details (under menu, different at each smartphone and tablet) and click “save route as GPX file.
Three methods are from here again the same.
Ensure that no destination or gpx routes are in the OSMAND open (close them all under the menu).
Go tot the menu and click directions. Select gpx route and select the track you just made.
It will load and then choose the the appropriate direction (as created or reverse).
Now you can follow that route.
The standard in OSMAND is the system language. You can switch that (temporarily) to English may be reducing confusion over the instructions.
Hope this is sufficient detail for you, success
Hugo