I have the plug-in that allows a selected area of the print bed to be excluded from printing during the print, for example this is great of one of the items detached from the bed or fails for some other reason.
Another option that this plug-in could be used for is to highlight an object on the bed in order to change print speed, but only for that object.
In the scenario where an item being printed has towers, threads, spikes or holes etc, these would all benefit from a slower print speed, while other items on the bed would not suffer in quality from being printed at a faster rate.
I know that I can print such a mix of items separately but wouldn't it be great to have them all printing at the same time, and all at the optimum speed for best quality?
Thank you.
What slicer do you use? Most slicers will let you apply different speeds to different objects.
Yes, I know. I use S3D so I can use different profiles, but often the need to change speed only happens at a specific layer height rather than the entire print.
One of the functions of a plugin such as I mentioned would have been the layer from which the speed change should take place.
Just an idea to get the best options for both quality and speed. For example, to be able to say that between layer x and layer y, for the selected object, print at this speed.
IMO, complex settings like this are best done in the slicer including changes at specific heights.
The plugin which allows an area on the print bed to be excluded is designed as a real-time "salvage" operation to save from having to abandon the entire print.
I agree, and it has proven to be very useful in the past. However, the ability to make gcode changes that would apply to only a selected area would, I believe, also be useful.
I don’t know how to write plugins but I have vb.net code for doing things to gcode files, including speed changes, so I just need to work out how to isolate a specific area of the bed.
Are you talking about https://github.com/paukstelis/OctoPrint-Cancelobject? If not, what plugin are you using?
How to write a plugin is well documented. You should have the sources for the plugin you are using and you appear to have source code to make the speed changes so it should be possible to merge the two.
Converting vb.net to Python should be relatively straight forward.
Yes, that’s the one.
I will look at the source for the cancel object plug-in. If it’s not dot.net I might have difficulties with it but if I can understand how it works I might be able to adapt something to suit.
Maybe my background as a Software Engineer (or my age) has biased my opinion but I believe that, for the most part, once you know one programming language, using another is a lot easier, particularly when you have example code.
That’s true. I learned most of what I know by reverse-engineering (and a
fair bit of Googling) 
I was actually a database engineer working with Oracle and SQL Server
enterprise systems (and a front end client CRM system called Vantive). I
only started working with dot.net in order to make tools for automating
repetitive tasks and debugging databases.