I think Workbench questions are best directed to @m_m
However @sho, you can upload a work-in-progress library via particle library upload
for your private use only. That way you can install it just as any other library.
Or the manual way without uploading first is to create a new project, add a lib
subfolder into which you copy <yourLibraryFolder>
.
After that you should have a project structure like that
.
│ project.properties
│ README.md
│
├───lib
│ └─── yourLibrary
│ │ library.properties
│ │ LICENSE
│ │ README.md
│ │
│ ├───examples
│ │ └───yourTest
│ │ project.properties
│ │ yourTest.ino
│ │
│ └───src
│ yourLibrary.cpp
│ yourLibrary.h
│
└───src
test.ino