How can one presently find out the status of solveable parameters other than looking at bookmark displays or setting cache policy to 100 (or have I missed yet another feature of the browser somewhere)?
If you know what your solvables are, you can look directly at the Parm node state records. There's a field called "funklet" in there, and it gives you the current value of the parameter (or the polynomial coeffs, if the Parm is a polc.)
Per default the funklet of a not solvable parm is not cached, however. For non-solvable parms you should set the field:
cache_funklet: default = False. Keep the funklet in memory, only affects non-solvable parms.
Also, if you add the table_name option to Parms, they'll store their values directly into an AIPS++ table which can be viewed with the aips++ tablebrowser.
Note that if a solver has 'last_update' set to True, a Parm node may appear to be empty after a solver has converged. The solver sends up one last "parm update" request (pu.* in the request id) after the solution has converged. This sets the parms to their final vaues. This is a "service request", so no numeric result is produced, and the result of the previous request is cleared from the cache.
The only way around it is to set bookmarks and/or have the nodes publish.