Ask HN: How do you go about building low code visual tools in 2021?

Seeing a lot of low code platforms being built that have a baked in capability to define a workflow for data and use case automation. I am wondering how does one go about building such workflow based engines in 2021?

Interested in understanding how to design the backend? Amazon seems to have its own state [language] (https://docs.aws.amazon.com/step-functions/latest/dg/concepts-amazon-states-language.html)

Any frameworks from OSS world that are dominating this space? Or just a collection of internal tooling exposed via APIs.

Any reference open architectures out there for backend and UI? Any theoretical concepts I need to revisit to get better at thinking about this? Finite State Machines modelling seems to be an obvious choice.

Some links:

AWS Step Functions :https://aws.amazon.com/blogs/aws/new-aws-step-functions-workflow-studio-a-low-code-visual-tool-for-building-state-machines/

Shopify Flow: https://apps.shopify.com/flow

Bubble: https://bubble.io/