Hi Jim,
Thanks for your interest in Syncfusion product.
We suggest you to use the overload method of activateTool which automatically deactivates the orthogonal tool once the connector is created. We have created the simple sample to demonstrate this and sample can be downloaded from the below link.
Here is the code snippet.
diagram.activateTool("orthogonalLine", true);
Here is the sample.
DrawOnce1530570158.zip
Please let me know if you have any quires.
Regards,
Kameshwaran R.