I had the same problem. Got a new laptop, reinstalled everything including eclipse and workbench.
Got my projects from git, and assumed I could rebuild my projects, which was not the case.
I also came across your previous post
being very annoyed I started to dig a bit. What I noticed was that the documentation pallet was not available in 12.2 unless I started Mathematica from eclips and the errors pointed to the lack of these tools. In the MathematicaSources of workbench the DocumentationTools and DocumentationBuild were present.
The build calls the system installation of Mathematica. So I copied these resources to the $BaseDirecotrory/applications of Mathematica and the build worked again. It also makes the documentation tools available again in the palettes.
Still trying to figure out some other issues with Workbench. One of the things that bug me most is that the documentation only finds functions in .m files while the preferred extension has been .wl for a while now.
Also when building HTML documentation for my website i have to run a very elaborate script to fix all the links and css styles.
Mathematica and workbench+eclipse have been the way I work for a very long time. In all these years workbench has only seen very few improvements. To be able to provide well-documented and integrated packages in Mathematica support and adequate documentation for this should definitely increase. Most of the things i learned about workbench and packages has been via nonofficial sources