Toolbox not backwards compatible

[cherkaue]

Was last compiled for ArcGIS Pro, so no longer works for ArcGIS Desktop. How long should we maintain backwards compatibility? Pro is essentially fully functional now, but some users still making use of Desktop. Could produce a secondary version of the toolset using https://pro.arcgis.com/en/pro-app/latest/tool-reference/data-management/savetoolboxtoversion.htm, which can save to older versions of the ArcGIS toolbox. That would at least provide some cross-platform compatibility until everyone is ready to retire desktop.