Changing the setting in the custom device profile is excellent. It determines resource allocation on the number tasks downloaded for each WCG subproject per device. But if that's not what you want Walkingrock (for example, you want to download enough work to crunch for half a day or one day at a time and that setting is too broad), then another way is to open up a plain text editor like Notepad or Notepad++ and saving a file named app_config.xml in the WCG project directory. On Windows, that would be C:\ProgramData\BOINC\projects\www.worldcommunitygrid.org\app_config.xml

Basic layout:

<app_config>
   <app>
      <name>name</name>
      <max_concurrent>N</max_concurrent>
   </app>
</app_config>

Change the "name" for each WCG subproject you want to control and "N" for the maximum number of tasks you want to run on that machine at a time.

* mip1 for Microbiome Immunity Project
* mcm1 for Mapping Cancer Markers
* hst1 for Help Stop TB
* scc1 for Smash Childhood Cancer
* arp1 for Africa Rainfall Project
* opn1 for OpenPandemics - COVID 19

Example to limit MIP1 to 2 and OPN1 to 5 and ARP1 to 1:

<app_config>
   <app>
      <name>mip1</name>
      <max_concurrent>2</max_concurrent>
   </app>
   <app>
      <name>opn1</name>
      <max_concurrent>5</max_concurrent>
   </app>
   <app>
      <name>arp1</name>
      <max_concurrent>1</max_concurrent>
   </app>
</app_config>

The project acronyms are actually part of the task names, albeit capitalized and always the characters before the first underscore.

OPN1_0001479_03008_0 02:59:44 (02:56:09) 98.00 98.702 00:02:21 6/3/2020 5:06:52 PM 6/10/2020 5:06:51 PM Running [15]

For app_config.xml write it out in small, it must be small as else it's not recognized by BOINC. Exception are the beta tasks. They are beta + a sequence number, the last beta28, which was the one for opn1.

I can manage with what I have.
Boinc has four choices, so I have different project mixes for 12 thread computers, 8 thread computers, 6 thread computers, and this laptop and another computer running at 50% to 60% power. As-is, the setting allows up to 64 of each project to run unless you have no maximum and only fill up the queue size. I wonder whether BOINC will ever come out with more than four device choices.

Does exist an official DTD for app_config.xml ?
Yves