Back in 2012, a VMware Fling was released called VIB Author, which allowed users to create their own custom vSphere Infrastructure Bundles (VIB) that typically would include configuration changes that was not possible when using the vSphere API such as enabling custom ESXi firewall ports or even bundling up custom utilities that could run within the ESXi Shell.
The VIB Author tool was eventually deprecated and removed due to the lack of support from Engineering, after all, it was released as a Fling. While the need for opening non-standard ESXi firewall port has greatly improved over the years, with the majority of 2nd and 3rd party solutions simply incorporating that into their solution offering, there are still use cases for requiring a custom VIB.
Even with the VIB Author Fling being deprecated, many in the community was still able to construct custom VIBs which were still compatible with later ESXi 5.x to 7.x releases. In fact, I even use the VIB Author to make it easier to distribute and install the popular ghettoVCB solution which can be installed using either a VIB or an Offline Bundle, another format the VIB Author tool supports creating.