It would be much helpful if additional tools to select entities like Nodes, Beams etc., in the polar coordinate system i.e., specifying the start and end radius (or diameter) and start and end angles. This helps a lot if we need to select the entities precisely in a structure created using polar coordinate system. The region selection tool may help a little but it doesn't provide the exact functionality required.
Thank you for posting this idea. It sounds interesting but quite niche. However I think you should be able to create a tool that meets your requirements using OpenSTAAD. That is exactly why OpenSTAAD exists. The logic should be fairly simple.
1) Create a loop for all node numbers,
2) compare their location against your requirements
3) If this matches, add to your node selection.