Scripting tools/PYTs: Add quick messages during tool run?

[AlfredBaldenweck]

Pretty simple: How do I add messages to the progress bar in the geoprocessing pane?

[DanPatterson · Accepted solution]

I haven't used it, but

SetProgressor—ArcGIS Pro | Documentation

looks promising

There are a few others in the general help area, like 

SetProgressorLabel—ArcGIS Pro | Documentation