I’d like to enable different tenants to start a process that is available to all of them. The only other way I can see to do this is to upload the same process multiple times with a tenantID. The link I gave seemed like an explanation of how to achieve this but confounded me within the first few sentences!!
In the configuration of the call-activity you can use a expression in the tenant field. So you can calculate what tenant to use based on a input mapping and then use the expression in the tenant config to get the value from the mapped local variable/variable from the input mapping.
Apologies for only spotting this nearly 2 years later! But for those still searching, we paid a Java contractor to write the code for this which looks surprisingly simple when you know what you are doing! The main thing to look out for is that if a user who starts a workflow belongs to more than one tenant then an override is needed in order for the correct tenant to be selected. What worked for us is to pass in a variable when starting a workflow which identifies the required tenant.