I recently started doing quite some UML / BPMN diagrams and of course wanted to use Confluence to write the analysis in.
There is of course draw.io but a plugin I started to love a lot for BPMN diagrams is Gliffy :
https://marketplace.atlassian.com/apps/254/gliffy-diagrams-for-confluence?tab=overview&hosting=cloud
I'm aware that we have new Community Guidelines that prohibit app vendors from putting promotional statements in posts (which is appreciated). However, since this post indirectly gives the impression that draw.io can't create BPMN diagrams, why don't you see for yourself how good we are at it: https://drawio-app.com/blog/using-draw-io-for-bpmn-diagrams/