Join Timout in Designer 7.1

Anyone try to set/use a variable from pipeline or document as timeout value in process? Designer 7.x has deprecated use of XPATH and global data instead providing 3 new methods: static values, Business calendar and some field value. The field value seem the only way now in 7.x to use some variable parameter to control timeouts but it seem to be always empty, no values are shown no mater what pipeline or selected documents are used inside the process. There is no documentation on how to set this value or how to use a parameter variable as timeout. It seem that 7.x only assume hardcoded static timeouts or some calendar values as timeouts.

The earlier issue with field value it seem to have a workaround to use simple variable in pipeline instead of document type for purpose of Timeout parameter values. Designer 7.1 seem cannot use document variable as timeout but can use a simple string variable if it appears i the step output definition.