@vpetrychuk and @MWulff,
There is a published REST API for updating estimates. The problem with using it is that it’s not yet available to Forge because it is also not available under OAuth 2. This doesn’t change the effect because I’m not aware whether/how it is possible to update estimates through only the Jira Platform APIs. But it does change the path to a solution.
As prior art:
I don’t see Jira Software on the Forge Roadmap but OAuth 2 for JSW is an open issue:
https://jira.atlassian.com/browse/JSWCLOUD-18874