This Bug is fixed in 13.1.1.2 just tested in my lab and now I can modify subroutine Settings without an error in the gui.
Here is the details from the release notes
726895 : VPE cannot modify subroutine settings
Component: Access Policy Manager
Symptoms:
Open per-request policy in Visual Policy Editor (VPE) that has a subroutine. Click 'Subroutine Settings / Rename.
Numeric values like the inactivity timeout are displayed as 'NaN. Attempts to modify the values results in MCP validation errors.
Conditions:
-- Per-request policy in the VPE.
-- Subroutine in the per-request policy.
-- Attempt to change the values.
Impact:
All fields say 'NaN', and error when trying to modify properties. Subroutine settings like the Inactivity Timeout and Gating Criteria cannot be modified through the VPE
Workaround:
Use tmsh to modify these values, for example:
tmsh modify apm policy access-policy subroutine properties modify { all { inactivity-timeout 301 } }
Fix:
The issue has been fixed; it is now possible to view and modify subroutine settings in the VPE.