I'm doing a lot of iterating inside a DOPnet, and even though the input data is static/not changing, I can't escape the painful first frame ‘Importing Data’ every single time I reset/rewind to the first frame.

Is this absolutely necessary if nothing outside the DOPnet is changing? The data coming in is cached RBD packed data with every piece both inactive and asleep.

Is there a flag that will freeze this, or do I have to resort to creating an initial .sim file?

Along those lines, is there a preference to keep a node from auto-processing when selected? And I'm not talking about activating for display; I mean straight up just selecting it to move it or change color or something.

–
mC

Is there a flag that will freeze this, or do I have to resort to creating an initial .sim file?

I don't think such a flag exist, you could use the first frame of .sim file as the start, but this workflow could become cumbersome quickly and I'm not sure you would get speed benefit ( needs to be tested on your specific setup )

node cooking on selection depends on a few things:
-if you have the geometry spreadsheet open it will cook any node selected to give you the data
-if you have a scene view open , you have to make sure "Show Display Operator" is on, and not "Show Current Operator" , which is default ( screenshot attached )

Bear in mind that when Show Current Operator is needed for viewport interactive tool such as paint etc