It sounds like you're looking for a Change Entity command. In the meantime...
To convert lines and arcs to polylines:
- Go to Curves, Polyline, Edit and toggle on Line to Poly.
Note: Toggle off Keep Lines if you do not want the original lines to remain.
- The prompt says, Select start point of polyline.
- Clicking on a line or arc will convert it to a polyline, and it will remain highlighted.
- You can continue clicking on additional entities while you're in this mode.
Note: You cannot select entities to convert by Area.
To 'add' a cover to a closed polyline:
- Go to Curves, Polyline, Edit and toggle on Toggle Cover.
- The prompt says, Select polyline to add/remove the cover.
- Clicking on a closed polyline will add or remove the cover.
- You can continue clicking on additional entities while you're in this mode.
Note: You cannot select polylines to edit by Area.
To add a fill to a polyline:
There are several ways to add a fill to a polyline.
Here is the primary method.
Note: Only closed polylines can be filled.
- Go to Hatching, SPB-Fill.
- Click on the polyline you would like to fill.
To add a knockout to a polyline:
- [CTRL] + Right-click on a polyline.
- Select KnockOut from the Context Menu.
To convert polylines to Smart Walls:
Note: It is not currently possible to convert lines and arcs to Smart Walls. They must be converted to polylines first.
- Go to Architect, make sure Auto 3D is toggled on, and select Edit Walls.
- Select Poly to Wall.
- The prompt says, Select polyline to convert to walls.
- Click on a polyline to convert it to a Smart Wall.
- The prompt says, Click a point to define the inside of the wall.
- Click on one side of the polyline to indicate the inside.
- You can continue selecting additional entities while you are in this mode.
To change the z-base and z-height settings for an entity or multiple entities:
- Go to Change, toggle on Z-base (and/or Z-height).
- Enter the new Z-base/height value.
- Toggle Entity to change one entity at a time.
- Toggle Area to draw a box that fully-contains all of the entities you would like to change.
- Press [CTRL] + [A] if you would like to select ALL entities (based on Layer Search).
To convert entities to a Symbol:
- Press [CTRL] + [E] to go to Clipboard Select.
- The prompt says, Select entity to Cut/Copy to the Clipboard.
- Click on an entity to highlight it.
- Continue clicking additional entities to add them to your selection.
- When you're finished selecting entities, select Copy.
Note: If Insert Pnt. was toggled on, the prompt will say, Enter the insertion point.
- Once you've copied the entities to the Clipboard, select the Edit pull-down menu.
- Select Paste As Symbol.
- The prompt says, Enter a name for this Symbol.
- You can enter a specific name, or accept the one that is automatically-generated.
- Place the symbol in your drawing.
Note: If you right-click before placing the symbol, it will still be available in the header of your drawing.
To convert a Symbol to an XREF:
- [CTRL] + Right-click on a symbol.
- Highlight Symbol Tools in the Context Menu, then select Convert to XREF.
- A File Dialog will appear.
- Enter a new name for the external file, or accept the default name.
- Select Save.
Note: To convert an XREF to a Symbol, select the Bind sub-menu in XREF Tools in the Context Menu.