OK, I know that Circle figure is a must, but it will appear later this year, as 2D circle needs to be able to handle cylinder, cone, sphere and dome in 3D (by user choice) and this requires a lot of coding.
For now, the Polygon is one alternative, but there could be a better – I will try to explain:
1. Make a Rectangle figure. Shape it to be a narrow horizontal rectangle with long side to be equal to the needed diameter and short side to be 1/5 of the diameter. I.e. if you need a 5” circle, make the rectangle 5” x 1”. See the dimensions in the status bar while shaping it.
2. Select then copy and paste the rectangle. While selected, rotate it at 90 degree, using “Objects” > “Rotate” command. You can directly hit the “90” or “-90” degree marks in the Rotate dialog box. Now you will have a cross figure.
3. Select the cross figure, then copy and paste it. While selected, rotate it at 45 degree.
4. Use immediately Paste again (Ctrl-V) and now turn the new cross to 22.5 degree. Again, paste the cross, but now turn it to -22.5 degree.
5. Select the whole figure and give it some height in the Properties, i.e. 1”. You can also group all the rectangles together for better handling. Now you will have a circle from rectangles in 2D and a pretty good cylinder in 3D.
If you decide, you can make the short side of the rectangle to be 1/10 of the long side (diameter) and with several more Copy/Paste/Rotate commands, you will receive a much smoother cylinder like the right one in the attached pictures. Not perfect, but better than nothing 
About the hole for the turntable – you can make as a valley example with lifting of the tracks level, otherwise it will not be visible.
I will take a look on the Millhouse turntables and will try to make a dedicated library for them.
Mixy
