Good question! a lot of people conflate custom software development as someone writing code, but it's really about building a system around how your software actually operates instead of forcing your workflows to fit a generic tool.
In practice that usually covers a few things:
Discovery/scoping — mapping out the actual workflow, data, and integration points before any code gets written
Architecture and build — designing something that fits your specific rules, permissions, and existing systems (not a one-size-fits-all template)
Integration — connecting it to whatever you already run (CRM, ERP, internal tools, etc.)
Deployment and support — shipping it safely and then maintaining/iterating as the development changes
The line I'd draw: if your workflow is common (email, accounting, video calls), off-the-shelf SaaS is almost always the better call. Custom software earns its cost when the workflow is specific to how you compete, or when you've outgrown what SaaS tools can flex to support.
We've worked with teams at TechnBrains on this exact discovery-to-deployment process, and the biggest thing that separates a good engagement from a bad one is usually how much time gets spent on that first scoping step, skip it and you end up with software that's technically custom but still doesn't fit how the team actually works.