I saw Chromium's build system and was amazed by the timeline view, for example:

https://ci.chromium.org/ui/p/chromium-m115/builders/ci/Win%20x64%20Builder/1286/timeline

(EDIT: link not working. Just go to Chromium's Gerrit, choose an active change, navigate to the "Checks" tab, and then click on one on the platforms on the left. The link takes you to their custom CI platform LUCI, which has a tab called "Timeline" which is what this is about.)

Coin could implement this in two components:

• Workitem timeline: each line represents one instruction, total width is the workitem duration
• Task timeline: each line represents one workitem, total width is the total duration of the task. It can contain "gaps" to show the waiting time for finding available VMs for the workitems.

P.S. Chromium's buildsystem UI (LUCI Milo) seems to be open source, with the timeline view documented here.