How to access related action of a record type using URL

If you are unable to utilize a!startProcessLink(), you can derive the URL utilizing fn!urlforrecord().  

Here the local!actionUrlPart is obtained by browsing to a record in the Appian interface, right clicking on the Related Action to copy the link.  The /actions/xyz portion will be the same for each record, per type and environment.

Then we replace the "/summary" portion with local!actionUrlPart for the full Related Action URL:

a!localVariables(
  local!actionUrlPart: "/actions/iwB1c1V7ZNiU85Gm1M6jYLcxIfUTYayREjSjNnOLVd_61xH5XDiI4JJMU0uPA",
  local!urlForRecord: urlforrecord(cons!YOUR_RECORD,308),
  replace(
    local!urlForRecord,
    search("/summary",local!urlForRecord,1),
    8,
    local!actionUrlPart
  )
)