What is the bug or the crash?
For instance, plugins that create and register a Custom Profile Source cannot see a corresponding custom node in the Elevation tree view anymore (in the current master, 3.99).
Expected behavior when registering a Custom Profile Source (like SwissLocator plugin does): the custom node at the top.

Steps to reproduce the issue
- Open a new project.
- Register a Custom Profile Source (e.g., by running this code snippet: https://gist.github.com/gacarrillor/4bb82379e4fa30df500c5532be1c9a13, you can verify the Python console, which prints
True if the Custom Profile Source was registered).
- Open an Elevation Profile widget.
Current result: The custom node is not in the Elevation layer tree.
Expected result with the code snippet provided above:
Versions
| QGIS version | 3.99.0-Master |
| QGIS code revision | f937ebdfd0b |
| |
| Libraries |
| Qt version | 6.9.2 |
| Python version | 3.13.7 |
| GDAL version | 3.10.3 |
| PROJ version | 9.6.0 |
| EPSG Registry database version | v12.004 (2025-03-02) |
| GEOS version | 3.13.1-CAPI-1.19.2 |
| SFCGAL version | No support |
| GeographicLib version | No support |
| SQLite version | 3.46.1 |
| PostgreSQL client version | 17.7 |
| SpatiaLite version | 5.1.0 |
| QWT version | 6.3.0 |
| QScintilla2 version | 2.14.1 |
| OS version | Ubuntu 25.10 |
| This copy of QGIS writes debugging output. |
| |
| Active Python plugins |
| AppendFeaturesToLayer | 3.0.0 |
| MetaSearch | 0.3.6 |
| a00_qpip | dev |
| db_manager | 0.1.20 |
| grassprovider | 2.12.99 |
| open_alaqs | dev |
| pg_service_parser | 0.9.0 |
| processing | 2.12.99 |
Supported QGIS version
New profile
Additional context
No response
What is the bug or the crash?
For instance, plugins that create and register a Custom Profile Source cannot see a corresponding custom node in the Elevation tree view anymore (in the current master, 3.99).
Expected behavior when registering a Custom Profile Source (like SwissLocator plugin does): the custom node at the top.

Steps to reproduce the issue
Trueif the Custom Profile Source was registered).Current result: The custom node is not in the Elevation layer tree.
Expected result with the code snippet provided above:
Versions
Supported QGIS version
New profile
Additional context
No response