Convert components selection to other components?

I've browsed through the Selection Tools section of the manual, but I'm unable to find an answer for my question.
Is it possible to convert selection of one type of components into another?
Something like Maya's PolySelectConvert command or Silo's Convert Selection To...?

Actually there are quite a few ways to convert selections! The easiest is: just switch to another component mode. The selection gets converted automatically, if suitable.
The documentation just gives a glimpse at what NVil can do, sadly. But as the software still progresses rather rapidly, it may be wise to wait a little bit with maintaining the documentation.

Unfortunately the "Selection Tools" section inside the app also doesn't give away all the selection conversions. (generally speaking, the order is a mess). Look inside the different component sections in the tools customization or use the tool search. You are even able to convert a polygon selection to just the border edges or vertices of that seletion. And other things, like selecting a vertex and converting the selection to all adjacent edges, like it is in Maya.

In vertex mode:
Edges By Selected Vertices
Edges In Selected Vertices
Polygons By Selected Vertices
Polygons In Selected Vertices

In edge mode:
Polygons By Selected Edges
Polygons In Selected Edges
Vertices Inside Edge Selection

In polygon mode:
Vertices Inside Polygon Selection
Vertices On Polygon Selection Border
Edges Inside Polygon Selection
Edges On Polygon Selection Border

i thought this was automatic since i got A S D bound to component types like silo and if i select a face than hit 'A' i get the 4 verts and the same with edges etc.

Well ASD conversion on component mode change that you've mentioned seems to be working very oddly. It sometimes converts components correctly and sometimes after component mode is changed, it remembers some previously selected components and instead converting the current selection it just displays those remembered. Sometimes it doesn't convert at all and deselects everything until I switch back to components which I've been converting from. It's like a gamble. Or there is no conversion on component switching going on at all.
I can upload a video that depicts this behaviour if you like.

Maybe it's some option I changed when I was exploring NVil's various menus and preferences? I'm puzzled.

You seem to have enabled 'Auto Restore Last Subobject Selection'. Go into any component mode (vertex/edge/polygon) and then in the menu 'Selection', you'll find it near the bottom of the entries. Turn it off.

That was it! It is all working now. I knew I've messed something up.
Thank you kind Sir. 

Well ASD conversion on component mode change that you've mentioned seems to be working very oddly. It sometimes converts components correctly and sometimes after component mode is changed, it remembers some previously selected components and instead converting the current selection it just displays those remembered. Sometimes it doesn't convert at all and deselects everything until I switch back to components which I've been converting from. It's like a gamble.
I can upload a video that depicts this behaviour if you like.

Maybe it's some option I changed when I was exploring NVil's various menus and preferences? I'm puzzled.

Make sure you have this option off: Selection > Auto Restore Last Subobject Selection.

There are cases that conversion will fail if the conversion is not perfect. For example, in vertex mode you have 5 vertices selected, 4 of them is the vertice of a quad poly and 1 of them does not belong to this quad poly. When you switch to polygon mode, the conversion will fail. You may expect that the quad poly should be selected automatically, but if it does, when you switch back to vertex mode, the vertex selection will be changed to 4 and that means you have lost your previous vertex selection.

I've just tested it and indeed - it happens. Is it intentional or something that will be fixed in the future?

It is intentional. The point is to keep selection intact. There are conversion commands if you don't get your expected result from the auto convert function.

Hi rubberDuck,

I've just tested it and indeed - it happens. Is it intentional or something that will be fixed in the future?

The sub-object auto-conversion works similar to other applications I have seen (such as Silo). If there are stray vertex in a selection, the conversion to polygons and back to vertex will not give you the same initial vertex selection.(as IStonia describes).

If you do need to keep sub_object selections before conversion (for example, to ensure stray vertex are saved/stored), you can use the "Subobject Group" command to store vertex/edges or polygon selections(Groups).

Okay, thanks. I'll keep this in mind.