Idea Delivered

Vendor re-assignment has now been released: https://community.rws.com/product-groups/trados-portfolio/cloud-offerings/b/blog/posts/trados-enterprise---23-06-1-release

Enabling multiple vendor assignments – Re-assigning vendors while project/workflow is active

You may have multiple vendors and you may not be able to set the workflow for one vendor specifically.
Therefore, you should be able to change vendors at a later stage. Especially, when the respective workflow step is already active.
You should be able to receive multiple quotes and choose the best option. The subsequent tasks for the other vendors that are not selected should be revoked/deleted.