Resolution:
By default, the maximum number of jobs (maxlistsize) in "Job Manager" to show on Workflow Desktop is 200.
You can increate the maximum job number by doing the following.
1) Open C:\tibco\bwworkflow\5.1\bui\archive\WEB-INF\portlet.xml,
2) search
&ltinit-param>
    &ltname&gtmaxlistsize</name>
    &ltvalue&gt200</value>
</init-param>
belonging to &ltportlet-name&gtjobmanager</portlet-name>
3) Change the value "200" to the number you want to show in Job Manager.
4) Undeploy all your BWWF projects.
5) Re-create BUIPlatform.war.
6) Re-deploy your BWWF applications.

This resolution also applies to Maximum Tasks.

Note: This maxlistsize value should not be given to a very big number because it may cause Workflow Desktop performance issue.