Is there a size limit of a workflow when trying to publish on Office 365?

There is a file size limitation within SharePoint Online that prevents files larger than 2 MB from being sent in one call to SharePoint. Because each action within the workflow design has a different "definition weight" (meaning that a Log to History action will have a smaller impact on the workflow size than a Query List action), there is no "hard" limit on the number of actions within the workflow design. As a best practice we recommend keeping workflow designs around 100 actions.

Nintex has added a number of enhancements to address the workflow size constraints above, including advanced compression, white space removal, and monitoring to alert the workflow publisher should the design they are attempting to publish approach this limit, so they can refactor the workflow, leverage component workflows for core reusable logic or perhaps split the design out into multiple workflows.