Want parent MENU_LOCAL_TASK tab to show when on a child page I have a set of local task menu items defined in my module. This includes the following items:


control => MENU_NORMAL_ITEM  
control/jobs => MENU_DEFAULT_LOCAL_TASK
control/jobs/% => MENU_???
control/download => MENU_LOCAL_TASK
control/settings => MENU_LOCAL_TASK


The three menu items (jobs, download and settings), display as tabs, as I want. When someone clicks through to see a particular job, I want this to show as having the jobs tab selected. 

If I add MENU_LOCAL_TASK to "control/jobs/%," the tabs show up, but I get notice errors (because Drupal is trying to define a link to % and can't know that).
If I don't, the specific job page does not have any tabs at the top.

Have I misunderstood anything? Can I achieve this in another way?
You can do what you want, but you need to change the url structure a bit. If I understand you correctly:


control/jobs: List of all jobs, should be MENU_NORMAL_ITEM 
control/jobs/%node (You should have a load function for the job, if not a node than something else), should be MENU_NORMAL_ITEM
control/jobs/%node/view:  MENU_DEFAULT_LOCAL_TASK (doesn't have  a callback)
control/jobs/%node/download: The download page for a specific job, MENU_LOCAL_TASK
control/jobs/%node/settings: The settings page for a specific job, MENU_LOCAL_TASK


You can take a look at the node and user module to get an idea on how create tabs in Drupal