I am trying to schedule the append geoprocessing tool with the 'Preserve Global IDs' environment variable set. When the tool is scheduled the global IDs are not preserved. If you look at the scheduled task calendar you can check that the 'Preserve Global ID' environment was not passed to the tool when scheduled to run.
I tried a few things in order to get something to work. The first thing was to uncheck and recheck the box next to Preserve Global IDs. When I schedule the tool, the details of the tool history did show that 'Preserve Global IDs' environment was used, but it was still not preserving global IDs.
Finally, I set up the append tool as a model in ModelBuilder. I had a feeling there was a bug in the environment hierarchy with regard to how environment variables are passed to scheduled tools. I unchecked and rechecked the box next to 'Preserve Global IDs' for the append tool within a model I had built and it did preserve the Global IDs once the model was scheduled to run.
It seems what is happening is that the defaults are overriding was is set in the environment panes unless they are refreshed by unchecking and rechecking the global ID box. Once the program detects a change in the environment pane it will pass them to the scheduled tool.
After further investigation the environment variables not carrying over under scheduled tasking is indeed a bug. I have been notified a patch has been made and this functionality will be availible in ArcGIS Pro 2.6.2.