I spent several years at a software development company that worked with the non-relational D3 database system, primarily in a database-specific language called D3 Basic (also known as Pick Basic or MV-Basic). While the company had been around for a while, the development tools it used had not kept pace with modern expectations. The primary
editor was used through a 80x24 character terminal environment. This non-standard terminal was a step-up from their previous system (the 'popular' line-based editor ed), but still a significant step down from something as advanced as the MS-DOS Editor.
There are commercially-available D3 Basic editors such as the one built into Accuterm. However, using these would have required the company to abandon its existing tools entirely and as such was not viable. Instead, I took the open-source SciTE editor and modified it heavily to handle both D3 Basic and interfacing with the D3 database, producing MVIDE. Despite its versions being named after Jean-Claude Van Damme films (the latest version is Hard Target) it has become an accepted development tool at that company.
MVIDE is written in C#, using Visual Studio 2015. It uses the Scintilla.Net library, and is based on the SciTE editor. It also uses Rocket Software's MVSP libraries to interface with the D3 database.
Early versions were heavily tied to the particular environment it was to be used in, relying on company-specific software. The latest version has no such requirements, and as such should work on any MVSP-enabled D3 database.
In the unlikely event you try it out, you will need to edit the MVIDE.exe.config file with the appropriate details. Feel free to get in touch if you have any issues with it!